{ "evaluation_id": "EVAL-20260402-150119", "question_id": "CODE-028", "question_text": "Your Node.js API is responding with 502 errors under load. Here's the relevant code and infrastructure:\n\n- Express.js API behind an Nginx reverse proxy\n- Connection pool to PostgreSQL (max 20 connections)\n- Average response time: 50ms normally, 30s+ during incidents\n- Error logs show: \"connect ETIMEDOUT\" and \"too many clients already\"\n- The issue starts when traffic exceeds 200 req/s\n\n```javascript\napp.get('/api/users/:id', async (req, res) => {\n const client = await pool.connect();\n const result = await client.query('SELECT * FROM users WHERE id = $1', [req.params.id]);\n res.json(result.rows[0]);\n});\n```\n\nWhat's wrong? Provide the fix and explain the connection pool exhaustion pattern.", "category": "code", "timestamp": "2026-04-02T15:01:19.871Z", "display_date": "Apr 02, 2026", "winner": { "name": "GPT-5.4", "provider": "openrouter", "score": 9.65 }, "avg_score": 9.044, "matrix_size": 89, "models_used": [ { "id": "claude_sonnet_46", "name": "Claude Sonnet 4.6", "provider": "openrouter" }, { "id": "grok_420", "name": "Grok 4.20", "provider": "openrouter" }, { "id": "deepseek_v4", "name": "DeepSeek V4", "provider": "openrouter" }, { "id": "gemini_3_flash", "name": "Gemini 3 Flash Preview", "provider": "Google" }, { "id": "minimax_m25", "name": "MiniMax M2.5", "provider": "openrouter" }, { "id": "mimo_v2_flash", "name": "MiMo-V2-Flash", "provider": "Xiaomi" }, { "id": "gpt_oss_120b", "name": "GPT-OSS-120B", "provider": "OpenAI" }, { "id": "claude_opus_46", "name": "Claude Opus 4.6", "provider": "openrouter" }, { "id": "gemini_31_pro", "name": "Gemini 3.1 Pro", "provider": "openrouter" }, { "id": "gpt_5_4", "name": "GPT-5.4", "provider": "openrouter" } ], "rankings": { "gpt_5_4": { "display_name": "GPT-5.4", "provider": "openrouter", "average_score": 9.65, "score_count": 9, "min_score": 9, "max_score": 10, "rank": 1 }, "claude_sonnet_46": { "display_name": "Claude Sonnet 4.6", "provider": "openrouter", "average_score": 9.61, "score_count": 9, "min_score": 8.55, "max_score": 10, "rank": 2 }, "grok_420": { "display_name": "Grok 4.20", "provider": "openrouter", "average_score": 9.26, "score_count": 9, "min_score": 8.55, "max_score": 9.8, "rank": 3 }, "minimax_m25": { "display_name": "MiniMax M2.5", "provider": "openrouter", "average_score": 9.17, "score_count": 9, "min_score": 7.95, "max_score": 9.8, "rank": 4 }, "gpt_oss_120b": { "display_name": "GPT-OSS-120B", "provider": "OpenAI", "average_score": 9.16, "score_count": 8, "min_score": 7.55, "max_score": 10, "rank": 5 }, "gemini_3_flash": { "display_name": "Gemini 3 Flash Preview", "provider": "Google", "average_score": 9.11, "score_count": 9, "min_score": 8.6, "max_score": 9.8, "rank": 6 }, "claude_opus_46": { "display_name": "Claude Opus 4.6", "provider": "openrouter", "average_score": 9, "score_count": 9, "min_score": 7.55, "max_score": 10, "rank": 7 }, "gemini_31_pro": { "display_name": "Gemini 3.1 Pro", "provider": "openrouter", "average_score": 8.71, "score_count": 9, "min_score": 7.6, "max_score": 9.6, "rank": 8 }, "deepseek_v4": { "display_name": "DeepSeek V4", "provider": "openrouter", "average_score": 8.49, "score_count": 9, "min_score": 7.45, "max_score": 9.6, "rank": 9 }, "mimo_v2_flash": { "display_name": "MiMo-V2-Flash", "provider": "Xiaomi", "average_score": 8.28, "score_count": 9, "min_score": 6.05, "max_score": 9.8, "rank": 10 } }, "judgments": [ { "judge_key": "gpt_oss_120b", "judge_name": "GPT-OSS-120B", "respondent_key": "claude_sonnet_46", "respondent_name": "Claude Sonnet 4.6", "weighted_score": 9.8, "brief_justification": "Accurately identifies the client leak, explains pool exhaustion, provides correct fixes, detailed production guidance, and actionable code/config snippets." }, { "judge_key": "gpt_oss_120b", "judge_name": "GPT-OSS-120B", "respondent_key": "grok_420", "respondent_name": "Grok 4.20", "weighted_score": 8.8, "brief_justification": "Accurately identifies connection leak, offers correct fix with finally/release and pool.query, explains exhaustion pattern, adds practical tuning and timeout advice." }, { "judge_key": "gpt_oss_120b", "judge_name": "GPT-OSS-120B", "respondent_key": "deepseek_v4", "respondent_name": "DeepSeek V4", "weighted_score": 8.25, "brief_justification": "Accurately identifies missing client.release, explains pool exhaustion, gives correct fix and practical recommendations, though could explore Nginx specifics more." }, { "judge_key": "gpt_oss_120b", "judge_name": "GPT-OSS-120B", "respondent_key": "gemini_3_flash", "respondent_name": "Gemini 3 Flash Preview", "weighted_score": 8.6, "brief_justification": "Accurately identifies the connection leak, explains pool exhaustion, offers correct code fixes and practical scaling advice, presented clearly and with useful detail." }, { "judge_key": "gpt_oss_120b", "judge_name": "GPT-OSS-120B", "respondent_key": "minimax_m25", "respondent_name": "MiniMax M2.5", "weighted_score": 8.8, "brief_justification": "Accurately identifies the connection leak, gives correct fix with proper release or pool.query, explains exhaustion pattern with calculations, and offers practical enhancements." }, { "judge_key": "gpt_oss_120b", "judge_name": "GPT-OSS-120B", "respondent_key": "mimo_v2_flash", "respondent_name": "MiMo-V2-Flash", "weighted_score": 8.55, "brief_justification": "Accurately identifies pool exhaustion and offers practical code and Nginx fixes; thorough coverage and clear presentation, though some minor technical phrasing could be sharper." }, { "judge_key": "mimo_v2_flash", "judge_name": "MiMo-V2-Flash", "respondent_key": "deepseek_v4", "respondent_name": "DeepSeek V4", "weighted_score": 8.6, "brief_justification": "Accurately identifies the connection leak, provides a correct fix with proper release, and explains the exhaustion pattern clearly. Offers useful additional recommendations." }, { "judge_key": "mimo_v2_flash", "judge_name": "MiMo-V2-Flash", "respondent_key": "gpt_oss_120b", "respondent_name": "GPT-OSS-120B", "weighted_score": 9.55, "brief_justification": "Accurate diagnosis of connection leak, comprehensive fix with multiple options, clear structure, insightful pattern explanation, and highly actionable guidance." }, { "judge_key": "gpt_5_4", "judge_name": "GPT-5.4", "respondent_key": "claude_opus_46", "respondent_name": "Claude Opus 4.6", "weighted_score": 7.55, "brief_justification": "Correctly identifies the core connection leak and explains the exhaustion pattern with appropriate fixes like release/finally and pool.query(). Some details are muddled or overstated, the response is duplicated/corrupted in places, and a few config recommendations are questionable or incomplete." }, { "judge_key": "gpt_5_4", "judge_name": "GPT-5.4", "respondent_key": "gemini_31_pro", "respondent_name": "Gemini 3.1 Pro", "weighted_score": 7.6, "brief_justification": "Correctly identifies the missing client.release() as the primary bug and gives proper fixes with pool.query/try-finally. Explanation of pool exhaustion is good, but the response is truncated and slightly overstates behavior (requests typically queue/time out rather than all crashed processes), so completeness is limited." }, { "judge_key": "gpt_5_4", "judge_name": "GPT-5.4", "respondent_key": "claude_sonnet_46", "respondent_name": "Claude Sonnet 4.6", "weighted_score": 8.55, "brief_justification": "Accurately identifies the unreleased pg client as the primary bug and explains the pool exhaustion cascade well. The fixes are clear and practical, especially using finally or pool.query(). Minor overreach on a few infrastructure claims (e.g. GC wording, some Nginx/min-pool guidance), but overall highly useful and thorough." }, { "judge_key": "gpt_5_4", "judge_name": "GPT-5.4", "respondent_key": "grok_420", "respondent_name": "Grok 4.20", "weighted_score": 8.55, "brief_justification": "Accurately identifies unreleased PostgreSQL clients as the primary issue and gives correct fixes with release/finally or pool.query. Clear explanation of pool exhaustion and practical mitigations. Minor overreach in attributing the shown code to leaks only on errors and in suggesting custom timeout middleware/ETIMEDOUT interpretation without more nuance." }, { "judge_key": "gpt_5_4", "judge_name": "GPT-5.4", "respondent_key": "deepseek_v4", "respondent_name": "DeepSeek V4", "weighted_score": 8.6, "brief_justification": "Accurately identifies the unreleased PostgreSQL client as the primary cause of pool exhaustion, explains the overload pattern clearly, and provides the correct try/finally fix with practical follow-up recommendations. Slightly incomplete because it could also mention using pool.query() directly for single queries and that 'too many clients already' may reflect aggregate DB connection pressure beyond just this one process." }, { "judge_key": "gpt_5_4", "judge_name": "GPT-5.4", "respondent_key": "gpt_oss_120b", "respondent_name": "GPT-OSS-120B", "weighted_score": 7.55, "brief_justification": "Correctly identifies the primary bug: leaked PostgreSQL clients due to missing release, and gives solid fixes with try/finally or pool.query. Good explanation of pool exhaustion and practical mitigations. However, it overstates a few details: ETIMEDOUT is not the typical pg pool timeout error, 'too many clients already' is more likely from multiple app instances or unreleased connections accumulating over time, and the concurrency math is confused. The answer is also truncated at the end." }, { "judge_key": "gpt_5_4", "judge_name": "GPT-5.4", "respondent_key": "gemini_3_flash", "respondent_name": "Gemini 3 Flash Preview", "weighted_score": 8.8, "brief_justification": "Accurately identifies the unreleased pg client as the main issue, explains the pool-exhaustion cascade clearly, and gives correct fixes with pool.query() or finally/client.release(). Minor overstatement around GC and exact timeout mechanics prevents a perfect score." }, { "judge_key": "gpt_5_4", "judge_name": "GPT-5.4", "respondent_key": "minimax_m25", "respondent_name": "MiniMax M2.5", "weighted_score": 7.95, "brief_justification": "Correctly identifies the main bug: unreleased pg clients causing pool exhaustion, and provides solid fixes and concurrency explanation. Clear and actionable. Minor inaccuracies: ETIMEDOUT and 502 causality are somewhat oversimplified, and claiming the driver may open connections beyond the configured pool max is misleading." }, { "judge_key": "gpt_5_4", "judge_name": "GPT-5.4", "respondent_key": "mimo_v2_flash", "respondent_name": "MiMo-V2-Flash", "weighted_score": 7.3, "brief_justification": "Identifies the main issue—a leaked DB client due to missing release—and gives a practical fix with pool.query/try-finally and timeouts. However, it incorrectly says await pool.connect() blocks the event loop, overstates some ETIMEDOUT and Postgres behavior, and includes speculative Nginx guidance that is not central to the root cause." }, { "judge_key": "claude_opus_46", "judge_name": "Claude Opus 4.6", "respondent_key": "gpt_5_4", "respondent_name": "GPT-5.4", "weighted_score": 9.8, "brief_justification": "The response correctly identifies the root cause (missing client.release()), provides both a proper fix with try/finally and the superior pool.query() alternative, thoroughly explains the connection pool exhaustion pattern step by step, connects all the symptoms (ETIMEDOUT, too many clients, 502s, latency spike) back to the root cause, and provides practical additional recommendations (pool timeouts, monitoring, single pool per process). The explanation is exceptionally well-structured with clea" }, { "judge_key": "claude_opus_46", "judge_name": "Claude Opus 4.6", "respondent_key": "gemini_31_pro", "respondent_name": "Gemini 3.1 Pro", "weighted_score": 8.4, "brief_justification": "The response correctly identifies the root cause (missing client.release()), provides two well-explained fixes with proper code examples, and begins a clear explanation of the cascading failure pattern. The diagnosis is accurate and the code fixes are correct. However, the response appears truncated mid-sentence in the cascade explanation (step 3 cuts off), missing the full chain through Nginx 502s, and it doesn't address other relevant aspects like tuning the pool size, Nginx proxy timeout conf" }, { "judge_key": "claude_opus_46", "judge_name": "Claude Opus 4.6", "respondent_key": "claude_sonnet_46", "respondent_name": "Claude Sonnet 4.6", "weighted_score": 9.55, "brief_justification": "The response accurately identifies the root cause (missing client.release()), explains the connection pool exhaustion pattern clearly with an excellent visual diagram, and provides a graduated set of fixes from immediate to production-ready. The inclusion of transaction patterns, nginx configuration, PostgreSQL tuning, pool monitoring, and the summary table makes it exceptionally complete and useful. Minor nitpick: the GC comment about connections being eventually released isn't quite accurate (" }, { "judge_key": "claude_opus_46", "judge_name": "Claude Opus 4.6", "respondent_key": "grok_420", "respondent_name": "Grok 4.20", "weighted_score": 9.35, "brief_justification": "The response correctly identifies the root cause (missing client.release() leading to connection pool exhaustion), provides two clean fixes with proper code examples, and thoroughly explains the cascading failure pattern. The additional recommendations (timeouts, pool tuning, monitoring) are practical and relevant. One minor nuance: the response could have noted that even in the happy path the original code never calls release(), not just on errors — though this is somewhat implied. The explanat" }, { "judge_key": "gpt_oss_120b", "judge_name": "GPT-OSS-120B", "respondent_key": "gpt_5_4", "respondent_name": "GPT-5.4", "weighted_score": 9.05, "brief_justification": "Accurately identifies the connection leak, gives correct fix with release or pool.query, explains exhaustion pattern in detail, and offers practical monitoring and config advice." }, { "judge_key": "claude_opus_46", "judge_name": "Claude Opus 4.6", "respondent_key": "deepseek_v4", "respondent_name": "DeepSeek V4", "weighted_score": 7.45, "brief_justification": "The response correctly identifies the core issue (missing client.release()) and provides a valid fix with try/catch/finally. However, it misses the simpler pool.query() alternative that handles connection management automatically, which is the idiomatic pg approach for simple queries. The explanation of the exhaustion pattern is accurate but could go deeper into the cascading failure mechanics (e.g., how Nginx proxy_read_timeout triggers 502s, how queued requests compound the problem). The addit" }, { "judge_key": "claude_opus_46", "judge_name": "Claude Opus 4.6", "respondent_key": "gpt_oss_120b", "respondent_name": "GPT-OSS-120B", "weighted_score": 10, "brief_justification": "The response perfectly identifies the root cause (missing client.release()), provides a thorough explanation of the connection pool exhaustion pattern with accurate math, offers two clean fix options (explicit try/finally and pool.query), and goes well beyond the minimum by covering query timeouts, pool configuration, back-pressure handling with 503 responses, and Nginx configuration. The formatting with tables, code blocks, and clear section headers makes it exceptionally readable. Every techni" }, { "judge_key": "claude_opus_46", "judge_name": "Claude Opus 4.6", "respondent_key": "gemini_3_flash", "respondent_name": "Gemini 3 Flash Preview", "weighted_score": 9.35, "brief_justification": "The response correctly identifies the root cause (missing client.release()), explains the cascading failure pattern clearly and accurately, provides both the pool.query() shorthand fix and the manual client.release() pattern with finally block, includes proper error handling, and adds useful capacity math and infrastructure recommendations. The throughput calculation (20 connections × 20 req/s = 400 req/s) is a nice touch. Minor nit: the explanation of ETIMEDOUT could be more precise (it's typic" }, { "judge_key": "claude_opus_46", "judge_name": "Claude Opus 4.6", "respondent_key": "minimax_m25", "respondent_name": "MiniMax M2.5", "weighted_score": 9.35, "brief_justification": "The response correctly identifies the root cause (missing client.release()), explains the connection pool exhaustion pattern with clear math (Little's Law), provides two clean fixes (try/finally with client.release and pool.query), and includes a comprehensive hardening table. The explanation of why 502s occur via Nginx upstream timeouts is accurate. Minor nit: the claim that the driver opens connections beyond the pool limit isn't quite right (pg Pool caps at max), but the overall diagnosis and" }, { "judge_key": "claude_opus_46", "judge_name": "Claude Opus 4.6", "respondent_key": "mimo_v2_flash", "respondent_name": "MiMo-V2-Flash", "weighted_score": 8.75, "brief_justification": "The response correctly identifies the primary bug: the missing `client.release()` call causing connection pool exhaustion, though it could have been more explicit and emphatic about this being THE critical bug rather than burying it among other concerns. The explanation of the cascading failure pattern is excellent and well-structured. The fix using `pool.query()` is correct and well-justified. The additional layers (Nginx config, concurrency limiter middleware) add practical value. Minor inaccu" }, { "judge_key": "gemini_31_pro", "judge_name": "Gemini 3.1 Pro", "respondent_key": "gpt_5_4", "respondent_name": "GPT-5.4", "weighted_score": 9.8, "brief_justification": "The response perfectly identifies the connection leak, provides the exact fix along with a better alternative, and thoroughly explains the exhaustion pattern, latency spikes, and proxy errors. It also includes excellent operational recommendations." }, { "judge_key": "gemini_31_pro", "judge_name": "Gemini 3.1 Pro", "respondent_key": "claude_opus_46", "respondent_name": "Claude Opus 4.6", "weighted_score": 8.1, "brief_justification": "Technical diagnosis is perfectly accurate with deep insights, but the response suffers from a major generation glitch in the middle and cuts off abruptly at the end." }, { "judge_key": "gemini_31_pro", "judge_name": "Gemini 3.1 Pro", "respondent_key": "claude_sonnet_46", "respondent_name": "Claude Sonnet 4.6", "weighted_score": 10, "brief_justification": "The response perfectly identifies the resource leak, provides multiple levels of fixes (immediate, best practice, production-ready), and offers excellent depth by covering transaction patterns and infrastructure tuning." }, { "judge_key": "gemini_31_pro", "judge_name": "Gemini 3.1 Pro", "respondent_key": "grok_420", "respondent_name": "Grok 4.20", "weighted_score": 9.55, "brief_justification": "" }, { "judge_key": "gemini_31_pro", "judge_name": "Gemini 3.1 Pro", "respondent_key": "deepseek_v4", "respondent_name": "DeepSeek V4", "weighted_score": 9.4, "brief_justification": "Accurately identifies the connection leak and provides a robust fix using try/finally. Explains the exhaustion pattern clearly and offers excellent actionable recommendations, though it misses suggesting `pool.query()` for single queries and doesn't fully explain the Postgres-side 'too many clients already' error." }, { "judge_key": "gemini_31_pro", "judge_name": "Gemini 3.1 Pro", "respondent_key": "gpt_oss_120b", "respondent_name": "GPT-OSS-120B", "weighted_score": 8.85, "brief_justification": "The response accurately identifies the connection leak and provides excellent, actionable solutions with deep technical context. However, the text cuts off abruptly at the end, slightly impacting completeness and clarity." }, { "judge_key": "gemini_31_pro", "judge_name": "Gemini 3.1 Pro", "respondent_key": "gemini_3_flash", "respondent_name": "Gemini 3 Flash Preview", "weighted_score": 9.8, "brief_justification": "Accurately identifies the connection leak, provides optimal and alternative code fixes with proper error handling, and explains the cascading failure mechanics clearly." }, { "judge_key": "gemini_31_pro", "judge_name": "Gemini 3.1 Pro", "respondent_key": "minimax_m25", "respondent_name": "MiniMax M2.5", "weighted_score": 8.6, "brief_justification": "Accurately identifies the connection leak and provides excellent solutions, including pool.query(). Good depth in explaining the exhaustion pattern. The response is slightly cut off at the end, impacting completeness." }, { "judge_key": "gemini_31_pro", "judge_name": "Gemini 3.1 Pro", "respondent_key": "mimo_v2_flash", "respondent_name": "MiMo-V2-Flash", "weighted_score": 6.05, "brief_justification": "" }, { "judge_key": "claude_sonnet_46", "judge_name": "Claude Sonnet 4.6", "respondent_key": "gpt_5_4", "respondent_name": "GPT-5.4", "weighted_score": 9.8, "brief_justification": "The response correctly identifies the root cause (missing client.release()), provides two well-structured fixes (try/finally and pool.query()), and delivers an excellent explanation of the connection pool exhaustion pattern with step-by-step breakdown. Covers all error messages from the logs, explains the 200 req/s threshold, and adds actionable recommendations for monitoring and configuration. Nearly flawless." }, { "judge_key": "claude_sonnet_46", "judge_name": "Claude Sonnet 4.6", "respondent_key": "claude_opus_46", "respondent_name": "Claude Opus 4.6", "weighted_score": 9.55, "brief_justification": "Excellent response that correctly identifies the connection leak bug, provides a detailed exhaustion timeline, and offers three levels of fixes from immediate to production-hardened. The visual timeline diagrams are particularly effective. Minor issue: the response appears to have a formatting artifact mid-way (duplicate content/truncation in the pool config section), but the core content is comprehensive and accurate. The withTransaction helper, pool monitoring, and configuration guidance add s" }, { "judge_key": "claude_sonnet_46", "judge_name": "Claude Sonnet 4.6", "respondent_key": "gemini_31_pro", "respondent_name": "Gemini 3.1 Pro", "weighted_score": 8.4, "brief_justification": "Correctly identifies the missing client.release() as the root cause and provides two solid fixes with good explanations. The connection pool exhaustion cascade is well-explained. Minor deductions for the truncated response (cut off mid-sentence at the end) and missing additional recommendations like pool sizing, connection timeouts, or Nginx upstream configuration that would address the full scope of the 502 errors under load." }, { "judge_key": "claude_sonnet_46", "judge_name": "Claude Sonnet 4.6", "respondent_key": "grok_420", "respondent_name": "Grok 4.20", "weighted_score": 9.35, "brief_justification": "Excellent response that correctly identifies the root cause (missing client.release() in error paths), provides multiple fix approaches with clear code examples, explains the exhaustion pattern thoroughly, and adds valuable additional recommendations like pool tuning and monitoring. The explanation of the cascade failure pattern is particularly insightful. Minor note: could mention connection poolers like PgBouncer for extreme scale scenarios." }, { "judge_key": "gpt_oss_120b", "judge_name": "GPT-OSS-120B", "respondent_key": "claude_opus_46", "respondent_name": "Claude Opus 4.6", "weighted_score": 8.8, "brief_justification": "Accurately pinpoints the missing client.release(), explains pool exhaustion, provides concrete fixes and robust configuration, all presented clearly and practically." }, { "judge_key": "gpt_oss_120b", "judge_name": "GPT-OSS-120B", "respondent_key": "gemini_31_pro", "respondent_name": "Gemini 3.1 Pro", "weighted_score": 9.05, "brief_justification": "Accurately identifies the missing client.release, offers correct fixes, explains the exhaustion pattern clearly, and provides actionable code examples." }, { "judge_key": "claude_sonnet_46", "judge_name": "Claude Sonnet 4.6", "respondent_key": "deepseek_v4", "respondent_name": "DeepSeek V4", "weighted_score": 8.05, "brief_justification": "Correctly identifies the missing client.release() as the root cause and provides a proper try/finally fix. Clear explanation of the exhaustion pattern. Could go deeper on pool sizing math (20 connections at 50ms = 400 req/s theoretical max, so something else may be contributing), idleTimeoutMillis configuration, using pool.query() directly to avoid manual release, and Nginx upstream timeout tuning. The additional recommendations are practical but somewhat generic." }, { "judge_key": "claude_sonnet_46", "judge_name": "Claude Sonnet 4.6", "respondent_key": "gpt_oss_120b", "respondent_name": "GPT-OSS-120B", "weighted_score": 9.55, "brief_justification": "Excellent response that correctly identifies the missing client.release() as the root cause, explains the exhaustion pattern clearly with a table and math, provides multiple fix options (Option A and B), adds production safeguards, and covers the Nginx layer. The math example is slightly simplified but directionally correct. Covers all relevant aspects including query timeouts, pool configuration, graceful degradation, and Nginx config. Highly actionable and well-structured." }, { "judge_key": "claude_sonnet_46", "judge_name": "Claude Sonnet 4.6", "respondent_key": "gemini_3_flash", "respondent_name": "Gemini 3 Flash Preview", "weighted_score": 9, "brief_justification": "Accurately identifies the connection leak as the root cause and explains the cascading failure pattern clearly. The fix using pool.query() is correct and well-explained, with the manual client fallback using finally block also provided. The scaling math is helpful and practical. Minor point: the garbage collector comment is slightly misleading (connections aren't released by GC in node-postgres without explicit release), but the overall diagnosis and solution are solid. Infrastructure recommenda" }, { "judge_key": "claude_sonnet_46", "judge_name": "Claude Sonnet 4.6", "respondent_key": "minimax_m25", "respondent_name": "MiniMax M2.5", "weighted_score": 9.8, "brief_justification": "Excellent response that correctly identifies the missing client.release() as the root cause, provides two clean fixes (try/finally and pool.query()), explains the exhaustion pattern with Little's Law math, and includes a comprehensive hardening table. The response is well-structured, technically accurate, and highly actionable." }, { "judge_key": "claude_sonnet_46", "judge_name": "Claude Sonnet 4.6", "respondent_key": "mimo_v2_flash", "respondent_name": "MiMo-V2-Flash", "weighted_score": 8.55, "brief_justification": "The response correctly identifies the core issue (missing client.release() causing connection leaks, plus pool exhaustion) and provides practical fixes. However, it misses the most critical bug in the original code: there's no try/finally block to ensure client.release() is called, which is the primary cause of connection leaks. The response focuses on switching to pool.query() as the fix without explicitly calling out this specific bug. The infrastructure fixes, exhaustion pattern explanation, " }, { "judge_key": "grok_420", "judge_name": "Grok 4.20", "respondent_key": "gpt_5_4", "respondent_name": "GPT-5.4", "weighted_score": 9, "brief_justification": "The response accurately identifies the core bug (missing client.release()), provides correct fixes with code, thoroughly explains the exhaustion pattern with clear stages, and adds valuable monitoring/config recommendations. Very complete, clear, and actionable." }, { "judge_key": "grok_420", "judge_name": "Grok 4.20", "respondent_key": "claude_opus_46", "respondent_name": "Claude Opus 4.6", "weighted_score": 8.8, "brief_justification": "Accurately identifies the core connection leak (missing release), provides clear timeline and diagrams, offers multiple levels of fixes including best practices and monitoring. Minor repetition and cutoff at the end slightly reduce completeness." }, { "judge_key": "grok_420", "judge_name": "Grok 4.20", "respondent_key": "gemini_31_pro", "respondent_name": "Gemini 3.1 Pro", "weighted_score": 8.6, "brief_justification": "The response accurately identifies the core connection leak, provides correct fixes with best practices, and explains the exhaustion cascade clearly. Minor incompleteness as it doesn't fully address Nginx/ETIMEDOUT symptoms or pool config tuning, but covers the primary issue thoroughly." }, { "judge_key": "grok_420", "judge_name": "Grok 4.20", "respondent_key": "claude_sonnet_46", "respondent_name": "Claude Sonnet 4.6", "weighted_score": 9, "brief_justification": "The response accurately identifies the main bug (missing release), explains the exhaustion pattern clearly with diagrams, provides multiple progressive fixes including best practices, adds production tuning for both Node and Nginx, and includes error handling and monitoring. It is thorough, well-structured, and highly actionable." }, { "judge_key": "grok_420", "judge_name": "Grok 4.20", "respondent_key": "deepseek_v4", "respondent_name": "DeepSeek V4", "weighted_score": 8.25, "brief_justification": "The response correctly identifies the missing client.release() as the primary bug causing pool exhaustion. It provides the standard try/finally pattern and good additional recommendations. Minor deduction for not mentioning that the shown code uses 'pg' Pool (which auto-releases on error in some versions) and for slightly oversimplifying the 502 cause (Nginx upstream timeout)." }, { "judge_key": "grok_420", "judge_name": "Grok 4.20", "respondent_key": "gpt_oss_120b", "respondent_name": "GPT-OSS-120B", "weighted_score": 9, "brief_justification": "The response accurately identifies the core bug (missing client.release()), explains the exhaustion pattern with a clear table and math, provides two robust fixes (with and without explicit connect), adds production safeguards, query timeouts, error handling, and Nginx config advice. Very thorough, well-structured, and actionable." }, { "judge_key": "grok_420", "judge_name": "Grok 4.20", "respondent_key": "gemini_3_flash", "respondent_name": "Gemini 3 Flash Preview", "weighted_score": 8.8, "brief_justification": "The response accurately identifies the connection leak as the core issue, provides correct fixes with code examples, explains the failure pattern and scaling math thoroughly, and offers practical infrastructure advice. Minor deduction for not addressing potential query queuing in pg-pool or Nginx timeout configs explicitly." }, { "judge_key": "grok_420", "judge_name": "Grok 4.20", "respondent_key": "minimax_m25", "respondent_name": "MiniMax M2.5", "weighted_score": 9, "brief_justification": "The response accurately identifies the missing client.release() as the core cause of pool exhaustion, provides both manual and simpler pool.query fixes with proper error handling, explains the throughput-latency math clearly, and includes practical hardening tips. Minor truncation at the end does not detract from overall value." }, { "judge_key": "grok_420", "judge_name": "Grok 4.20", "respondent_key": "mimo_v2_flash", "respondent_name": "MiMo-V2-Flash", "weighted_score": 7.8, "brief_justification": "The response correctly identifies pool exhaustion and provides a good fix using pool.query() with timeouts, but incorrectly claims await pool.connect() is 'synchronous in nature' and that it blocks the event loop (it's async). The exhaustion pattern explanation is mostly accurate but has some technical inaccuracies regarding timeouts and leaks. Overall thorough and well-structured." }, { "judge_key": "deepseek_v4", "judge_name": "DeepSeek V4", "respondent_key": "gpt_5_4", "respondent_name": "GPT-5.4", "weighted_score": 9.6, "brief_justification": "Accurate, thorough, and actionable with excellent depth and clarity." }, { "judge_key": "deepseek_v4", "judge_name": "DeepSeek V4", "respondent_key": "claude_opus_46", "respondent_name": "Claude Opus 4.6", "weighted_score": 9.8, "brief_justification": "Accurate, thorough, and practical with excellent depth and clarity." }, { "judge_key": "deepseek_v4", "judge_name": "DeepSeek V4", "respondent_key": "gemini_31_pro", "respondent_name": "Gemini 3.1 Pro", "weighted_score": 9.2, "brief_justification": "Accurate diagnosis, clear fixes, and insightful explanation of connection pool exhaustion." }, { "judge_key": "deepseek_v4", "judge_name": "DeepSeek V4", "respondent_key": "claude_sonnet_46", "respondent_name": "Claude Sonnet 4.6", "weighted_score": 9.8, "brief_justification": "Comprehensive and accurate analysis with multiple practical fixes." }, { "judge_key": "deepseek_v4", "judge_name": "DeepSeek V4", "respondent_key": "grok_420", "respondent_name": "Grok 4.20", "weighted_score": 9.8, "brief_justification": "Accurate, thorough, and actionable with excellent clarity and depth." }, { "judge_key": "deepseek_v4", "judge_name": "DeepSeek V4", "respondent_key": "gpt_oss_120b", "respondent_name": "GPT-OSS-120B", "weighted_score": 10, "brief_justification": "Comprehensive, accurate, and actionable response with clear explanations and fixes." }, { "judge_key": "deepseek_v4", "judge_name": "DeepSeek V4", "respondent_key": "gemini_3_flash", "respondent_name": "Gemini 3 Flash Preview", "weighted_score": 8.8, "brief_justification": "Accurate diagnosis and solution with clear explanation of connection leaks and pool exhaustion." }, { "judge_key": "deepseek_v4", "judge_name": "DeepSeek V4", "respondent_key": "minimax_m25", "respondent_name": "MiniMax M2.5", "weighted_score": 9.8, "brief_justification": "Accurate, thorough, and clear explanation with actionable fixes and deep analysis." }, { "judge_key": "deepseek_v4", "judge_name": "DeepSeek V4", "respondent_key": "mimo_v2_flash", "respondent_name": "MiMo-V2-Flash", "weighted_score": 9.8, "brief_justification": "Comprehensive, accurate, and actionable response with deep analysis." }, { "judge_key": "gemini_3_flash", "judge_name": "Gemini 3 Flash Preview", "respondent_key": "gpt_5_4", "respondent_name": "GPT-5.4", "weighted_score": 10, "brief_justification": "The response perfectly identifies the root cause (connection leak), provides the standard fix (try/finally/release), offers a superior alternative (pool.query), and explains the cascading failure pattern in detail." }, { "judge_key": "gemini_3_flash", "judge_name": "Gemini 3 Flash Preview", "respondent_key": "claude_opus_46", "respondent_name": "Claude Opus 4.6", "weighted_score": 9.8, "brief_justification": "The response correctly identifies the connection leak as the root cause. It provides a clear timeline of how the exhaustion occurs, offers multiple levels of fixes (from simple to production-hardened), and includes essential monitoring and transaction patterns. The explanation of why the 502 occurs (Nginx timeout vs DB timeout) is spot on." }, { "judge_key": "gemini_3_flash", "judge_name": "Gemini 3 Flash Preview", "respondent_key": "gemini_31_pro", "respondent_name": "Gemini 3.1 Pro", "weighted_score": 9.6, "brief_justification": "The response perfectly identifies the connection leak caused by the missing client.release() call. It provides the two standard industry fixes (pool.query and try/finally) and accurately explains the cascading failure pattern that leads to the 502 errors." }, { "judge_key": "gemini_3_flash", "judge_name": "Gemini 3 Flash Preview", "respondent_key": "claude_sonnet_46", "respondent_name": "Claude Sonnet 4.6", "weighted_score": 10, "brief_justification": "This is an exceptional response. It correctly identifies the resource leak (missing client.release()), explains the exhaustion pattern with a clear diagram, provides multiple levels of fixes (from immediate to production-ready), and even includes infrastructure-level tuning for Nginx and PostgreSQL. The distinction between pool.query() and pool.connect() is crucial and well-explained." }, { "judge_key": "gemini_3_flash", "judge_name": "Gemini 3 Flash Preview", "respondent_key": "grok_420", "respondent_name": "Grok 4.20", "weighted_score": 9.8, "brief_justification": "The response perfectly identifies the root cause: the code acquires a client but never releases it, leading to a connection leak. It provides two valid fixes, explains the exhaustion pattern clearly, and offers additional production-ready advice like setting connection timeouts." }, { "judge_key": "gemini_3_flash", "judge_name": "Gemini 3 Flash Preview", "respondent_key": "deepseek_v4", "respondent_name": "DeepSeek V4", "weighted_score": 9.6, "brief_justification": "The response correctly identifies the primary issue (connection leak) and provides the industry-standard fix using a try/finally block. It accurately explains the exhaustion pattern and offers relevant infrastructure advice." }, { "judge_key": "gemini_3_flash", "judge_name": "Gemini 3 Flash Preview", "respondent_key": "minimax_m25", "respondent_name": "MiniMax M2.5", "weighted_score": 9.6, "brief_justification": "The response perfectly identifies the root cause (connection leak due to missing release), provides the standard fix using try/finally, and offers the optimized pool.query alternative. It correctly explains the math behind the exhaustion and provides actionable hardening tips. The response cut off slightly at the very end ('Grace'), but the core content is complete." }, { "judge_key": "gemini_3_flash", "judge_name": "Gemini 3 Flash Preview", "respondent_key": "mimo_v2_flash", "respondent_name": "MiMo-V2-Flash", "weighted_score": 9.15, "brief_justification": "The response correctly identifies the primary issue: the provided code snippet acquires a client but never releases it, leading to a connection leak. It provides a robust fix using pool.query() and adds valuable infrastructure-level advice (Nginx and timeouts) to handle backpressure." }, { "judge_key": "minimax_m25", "judge_name": "MiniMax M2.5", "respondent_key": "gpt_5_4", "respondent_name": "GPT-5.4", "weighted_score": 10, "brief_justification": "Excellent response that correctly identifies the connection leak, provides two proper fixes, and thoroughly explains the pool exhaustion pattern including why 200 req/s triggers it, how latency explodes, and the cascade of errors (502, ETIMEDOUT, too many clients). Includes valuable additional recommendations for monitoring and prevention." }, { "judge_key": "minimax_m25", "judge_name": "MiniMax M2.5", "respondent_key": "claude_opus_46", "respondent_name": "Claude Opus 4.6", "weighted_score": 8.6, "brief_justification": "Accurately identifies the connection leak as root cause. Provides comprehensive three-level fix with code examples. Explains exhaustion timeline clearly with diagrams. Includes production-hardened pool configuration and monitoring. Slight duplication in response slightly reduces clarity but overall excellent technical depth and actionable guidance." }, { "judge_key": "minimax_m25", "judge_name": "MiniMax M2.5", "respondent_key": "gemini_31_pro", "respondent_name": "Gemini 3.1 Pro", "weighted_score": 8.9, "brief_justification": "Accurately identifies the connection leak and provides correct fixes. Well-structured with clear code examples. Explains the exhaustion pattern well. Minor deduction for incomplete final sentence and slight room for more depth on monitoring/mitigation." }, { "judge_key": "minimax_m25", "judge_name": "MiniMax M2.5", "respondent_key": "claude_sonnet_46", "respondent_name": "Claude Sonnet 4.6", "weighted_score": 10, "brief_justification": "Excellent response that correctly identifies the resource leak, provides multiple layered fixes (try/finally, pool.query(), production-ready), explains the exhaustion pattern visually, covers infrastructure tuning, and includes monitoring. Comprehensive and actionable." }, { "judge_key": "minimax_m25", "judge_name": "MiniMax M2.5", "respondent_key": "grok_420", "respondent_name": "Grok 4.20", "weighted_score": 8.8, "brief_justification": "Accurately identifies connection pool exhaustion as the root cause with correct explanation of the leak pattern. Provides two solid fix options with code examples. Covers additional important aspects like timeouts and pool tuning. Well-structured and highly actionable." }, { "judge_key": "minimax_m25", "judge_name": "MiniMax M2.5", "respondent_key": "deepseek_v4", "respondent_name": "DeepSeek V4", "weighted_score": 8.25, "brief_justification": "Accurately identifies connection pool exhaustion as root cause. Fix is correct using try/finally pattern. Well-structured explanation covers the mechanism and provides actionable recommendations. Slight deduction for depth - could elaborate more on Nginx timeout relationship to 502s." }, { "judge_key": "minimax_m25", "judge_name": "MiniMax M2.5", "respondent_key": "gpt_oss_120b", "respondent_name": "GPT-OSS-120B", "weighted_score": 8.8, "brief_justification": "Accurately identifies the missing client.release() as root cause. Provides clear explanation of connection pool exhaustion pattern with step-by-step breakdown. Offers two correct fix options (finally block and pool.query) plus additional safeguards. Well-structured with code examples, tables, and mathematical explanation of why failure occurs at ~200 req/s. Highly actionable with production-ready code." }, { "judge_key": "minimax_m25", "judge_name": "MiniMax M2.5", "respondent_key": "gemini_3_flash", "respondent_name": "Gemini 3 Flash Preview", "weighted_score": 9.25, "brief_justification": "Accurately identifies the connection leak as root cause, explains the cascading failure pattern with correct throughput math, provides both immediate fix (pool.query()) and proper manual release pattern, and includes infrastructure recommendations. Well-structured with clear code examples." }, { "judge_key": "minimax_m25", "judge_name": "MiniMax M2.5", "respondent_key": "mimo_v2_flash", "respondent_name": "MiMo-V2-Flash", "weighted_score": 8.55, "brief_justification": "Accurate diagnosis of connection pool exhaustion with good explanation of the failure cascade. Provides practical code and infrastructure fixes. Slightly misses explicitly calling out the connection leak (missing client.release()) in the original code, but the pool.query() recommendation would fix this. Well-structured and comprehensive." }, { "judge_key": "mimo_v2_flash", "judge_name": "MiMo-V2-Flash", "respondent_key": "gpt_5_4", "respondent_name": "GPT-5.4", "weighted_score": 9.8, "brief_justification": "Accurate diagnosis of connection leak, comprehensive fix options, clear explanation of exhaustion pattern, and actionable recommendations." }, { "judge_key": "mimo_v2_flash", "judge_name": "MiMo-V2-Flash", "respondent_key": "claude_opus_46", "respondent_name": "Claude Opus 4.6", "weighted_score": 10, "brief_justification": "Comprehensive, accurate diagnosis with clear fixes, timeline, and production-hardened configuration." }, { "judge_key": "mimo_v2_flash", "judge_name": "MiMo-V2-Flash", "respondent_key": "gemini_31_pro", "respondent_name": "Gemini 3.1 Pro", "weighted_score": 8.6, "brief_justification": "Accurate diagnosis of connection leak, provides two clear fixes with code, explains exhaustion pattern well." }, { "judge_key": "mimo_v2_flash", "judge_name": "MiMo-V2-Flash", "respondent_key": "claude_sonnet_46", "respondent_name": "Claude Sonnet 4.6", "weighted_score": 9.8, "brief_justification": "Comprehensive, accurate, and actionable analysis with multiple fixes and infrastructure tuning." }, { "judge_key": "mimo_v2_flash", "judge_name": "MiMo-V2-Flash", "respondent_key": "grok_420", "respondent_name": "Grok 4.20", "weighted_score": 9.35, "brief_justification": "Accurate diagnosis of connection leak, provides clear fixes with code, explains exhaustion pattern, and offers actionable additional steps." }, { "judge_key": "mimo_v2_flash", "judge_name": "MiMo-V2-Flash", "respondent_key": "gemini_3_flash", "respondent_name": "Gemini 3 Flash Preview", "weighted_score": 9.6, "brief_justification": "The response accurately identifies the connection leak as the root cause, provides the correct fix (pool.query or finally block), and explains the exhaustion pattern clearly. It also includes a useful infrastructure recommendation." }, { "judge_key": "mimo_v2_flash", "judge_name": "MiMo-V2-Flash", "respondent_key": "minimax_m25", "respondent_name": "MiniMax M2.5", "weighted_score": 9.6, "brief_justification": "Response accurately identifies the connection leak, provides correct fixes with code examples, explains the exhaustion pattern clearly, and offers actionable additional tips." } ], "meta": { "source": "The Multivac (app.themultivac.com)", "methodology": "10x10 blind peer matrix evaluation", "criteria": "correctness, completeness, clarity, depth, usefulness", "self_judgments": "excluded from rankings", "license": "Open data — cite as: The Multivac (2026)" } }