{ "evaluation_id": "EVAL-20260315-034630", "question_id": "EVAL-20260315-034630", "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": "2026-03-15T03:46:30.217Z", "display_date": "Mar 15, 2026", "winner": { "name": "Kimi K2.5", "provider": "openrouter", "score": 9.57 }, "avg_score": 8.97, "matrix_size": 83, "models_used": [ { "id": "kimi_k25", "name": "Kimi K2.5", "provider": "openrouter" }, { "id": "devstral", "name": "Devstral Small", "provider": "openrouter" }, { "id": "gemma3_27b", "name": "Gemma 3 27B", "provider": "openrouter" }, { "id": "llama4_scout", "name": "Llama 4 Scout", "provider": "openrouter" }, { "id": "phi4", "name": "Phi-4 14B", "provider": "openrouter" }, { "id": "granite_40", "name": "Granite 4.0 Micro", "provider": "openrouter" }, { "id": "qwen3_8b", "name": "Qwen 3 8B", "provider": "openrouter" }, { "id": "mistral_nemo", "name": "Mistral Nemo 12B", "provider": "openrouter" }, { "id": "llama31_8b", "name": "Llama 3.1 8B", "provider": "openrouter" }, { "id": "qwen3_32b", "name": "Qwen 3 32B", "provider": "openrouter" } ], "rankings": { "kimi_k25": { "display_name": "Kimi K2.5", "provider": "openrouter", "average_score": 9.57, "score_count": 9, "min_score": 8.8, "max_score": 10, "rank": 1 }, "gemma3_27b": { "display_name": "Gemma 3 27B", "provider": "openrouter", "average_score": 9.48, "score_count": 8, "min_score": 8.8, "max_score": 9.8, "rank": 2 }, "qwen3_8b": { "display_name": "Qwen 3 8B", "provider": "openrouter", "average_score": 9.45, "score_count": 8, "min_score": 8.8, "max_score": 10, "rank": 3 }, "phi4": { "display_name": "Phi-4 14B", "provider": "openrouter", "average_score": 9.09, "score_count": 8, "min_score": 8.15, "max_score": 10, "rank": 4 }, "mistral_nemo": { "display_name": "Mistral Nemo 12B", "provider": "openrouter", "average_score": 9, "score_count": 8, "min_score": 7.95, "max_score": 9.8, "rank": 5 }, "granite_40": { "display_name": "Granite 4.0 Micro", "provider": "openrouter", "average_score": 8.94, "score_count": 8, "min_score": 8.05, "max_score": 10, "rank": 6 }, "devstral": { "display_name": "Devstral Small", "provider": "openrouter", "average_score": 8.81, "score_count": 8, "min_score": 8.2, "max_score": 9.4, "rank": 7 }, "qwen3_32b": { "display_name": "Qwen 3 32B", "provider": "openrouter", "average_score": 8.78, "score_count": 8, "min_score": 7.85, "max_score": 9.8, "rank": 8 }, "llama4_scout": { "display_name": "Llama 4 Scout", "provider": "openrouter", "average_score": 8.66, "score_count": 9, "min_score": 5.75, "max_score": 9.8, "rank": 9 }, "llama31_8b": { "display_name": "Llama 3.1 8B", "provider": "openrouter", "average_score": 7.93, "score_count": 9, "min_score": 3, "max_score": 9.2, "rank": 10 } }, "judgments": [ { "judge_key": "qwen3_32b", "judge_name": "Qwen 3 32B", "respondent_key": "kimi_k25", "respondent_name": "Kimi K2.5", "weighted_score": 9.55, "brief_justification": "The response accurately identifies the connection pool leak issue, provides multiple solutions, and explains the exhaustion pattern in detail. It includes code examples, timing analysis, and additional hardening measures. The explanation is clear, well-structured, and offers valuable insights beyond the surface-level problem." }, { "judge_key": "qwen3_32b", "judge_name": "Qwen 3 32B", "respondent_key": "devstral", "respondent_name": "Devstral Small", "weighted_score": 8.4, "brief_justification": "Correctly identifies connection pool exhaustion and provides a code fix with proper connection release. Explains the pattern and recommends optimizations like indexing and caching. Could improve by explicitly mentioning PostgreSQL's `max_connections` limit and how it interacts with the pool size." }, { "judge_key": "qwen3_32b", "judge_name": "Qwen 3 32B", "respondent_key": "gemma3_27b", "respondent_name": "Gemma 3 27B", "weighted_score": 9.6, "brief_justification": "The response accurately identifies connection pool exhaustion and query performance issues as root causes. It provides a structured diagnosis, explains the exhaustion pattern in detail, and offers practical fixes including code examples. The explanation is clear, actionable, and addresses both immediate and systemic improvements." }, { "judge_key": "qwen3_32b", "judge_name": "Qwen 3 32B", "respondent_key": "llama4_scout", "respondent_name": "Llama 4 Scout", "weighted_score": 9.05, "brief_justification": "The response correctly identifies the missing client.release() as the root cause of connection pool exhaustion, provides a precise fix with a try-catch-finally block, and explains the pattern with actionable recommendations. It thoroughly addresses the 502 errors and traffic bottleneck while maintaining clear structure and practical insights." }, { "judge_key": "qwen3_32b", "judge_name": "Qwen 3 32B", "respondent_key": "phi4", "respondent_name": "Phi-4 14B", "weighted_score": 8.8, "brief_justification": "The response correctly identifies connection pool exhaustion as the root cause and provides a precise fix by adding `client.release()`. It explains the exhaustion pattern clearly and offers actionable recommendations. The only minor omission is not explicitly mentioning that the 502 errors are a symptom of upstream failures (Express not responding), but the explanation is still accurate and practical." }, { "judge_key": "qwen3_32b", "judge_name": "Qwen 3 32B", "respondent_key": "granite_40", "respondent_name": "Granite 4.0 Micro", "weighted_score": 8.35, "brief_justification": "The response correctly identifies connection pool exhaustion as the root cause and explains the pattern. It provides practical solutions like increasing pool size and implementing timeouts. However, it misses the critical point that the code doesn't release database connections after use, which is a major contributor to the issue." }, { "judge_key": "qwen3_32b", "judge_name": "Qwen 3 32B", "respondent_key": "qwen3_8b", "respondent_name": "Qwen 3 8B", "weighted_score": 9.6, "brief_justification": "The response accurately identifies connection leaks and pool/database configuration mismatches as root causes, provides precise code fixes with explanations, and thoroughly explains the exhaustion pattern. It balances technical depth with actionable solutions." }, { "judge_key": "qwen3_32b", "judge_name": "Qwen 3 32B", "respondent_key": "mistral_nemo", "respondent_name": "Mistral Nemo 12B", "weighted_score": 7.95, "brief_justification": "Correctly identifies connection pool exhaustion and Nginx timeout issues, but misses the critical code-level fix (missing client.release() in error handling). Solutions like pool size adjustment, timeout configuration, and caching are valid, though deeper analysis of the code structure's potential to leak connections would improve completeness." }, { "judge_key": "qwen3_32b", "judge_name": "Qwen 3 32B", "respondent_key": "llama31_8b", "respondent_name": "Llama 3.1 8B", "weighted_score": 8.4, "brief_justification": "Correctly identifies connection pool exhaustion and provides a working fix with `pool.release()`. The explanation of error patterns is accurate, but the original code's missing `release` is not explicitly called out as the root cause. Recommendations are practical but lack deeper analysis of concurrency patterns." }, { "judge_key": "kimi_k25", "judge_name": "Kimi K2.5", "respondent_key": "llama4_scout", "respondent_name": "Llama 4 Scout", "weighted_score": 5.75, "brief_justification": "The response correctly identifies pool exhaustion but fundamentally misunderstands the bug: the original code never releases connections (connection leak), not that it releases them 'slowly.' It also misses that pool.query() is the better pattern for single queries and fails to explain the mathematical proof (200 req/s × 50ms = 10 concurrent connections, well under the 20 limit, proving it's a leak not capacity) or the Nginx timeout correlation." }, { "judge_key": "kimi_k25", "judge_name": "Kimi K2.5", "respondent_key": "llama31_8b", "respondent_name": "Llama 3.1 8B", "weighted_score": 3, "brief_justification": "The response fails to identify the critical bug in the original code (missing client.release()) and provides incorrect syntax in the fix (pool.release(client) should be client.release()). Increasing pool size without fixing the connection leak only delays the exhaustion. The explanation of the exhaustion pattern is superficial and incorrectly attributes ETIMEDOUT to Nginx rather than pool acquisition timeouts." }, { "judge_key": "devstral", "judge_name": "Devstral Small", "respondent_key": "qwen3_32b", "respondent_name": "Qwen 3 32B", "weighted_score": 9.05, "brief_justification": "The response correctly identifies the missing `client.release()` as the root cause and explains the connection pool exhaustion pattern. It provides a clear breakdown of the problem and its impact on the system under load. The explanation is insightful and actionable, though it could benefit from a brief mention of how to properly handle errors and edge cases." }, { "judge_key": "devstral", "judge_name": "Devstral Small", "respondent_key": "kimi_k25", "respondent_name": "Kimi K2.5", "weighted_score": 10, "brief_justification": "The response accurately identifies the connection pool leak, explains the exhaustion pattern, provides clear fixes, and offers additional hardening tips." }, { "judge_key": "devstral", "judge_name": "Devstral Small", "respondent_key": "gemma3_27b", "respondent_name": "Gemma 3 27B", "weighted_score": 9.8, "brief_justification": "The response provides a thorough and accurate diagnosis of the connection pool exhaustion issue, along with a detailed, actionable fix. It also explains the connection pool exhaustion pattern clearly and comprehensively." }, { "judge_key": "devstral", "judge_name": "Devstral Small", "respondent_key": "llama4_scout", "respondent_name": "Llama 4 Scout", "weighted_score": 8.6, "brief_justification": "The response accurately identifies the connection pool exhaustion issue and provides a clear, actionable fix. It also explains the pattern and offers additional recommendations, though some points could be more concise." }, { "judge_key": "devstral", "judge_name": "Devstral Small", "respondent_key": "phi4", "respondent_name": "Phi-4 14B", "weighted_score": 8.8, "brief_justification": "The response accurately identifies the connection pool exhaustion issue and provides a clear, actionable fix with additional recommendations for improvement." }, { "judge_key": "devstral", "judge_name": "Devstral Small", "respondent_key": "granite_40", "respondent_name": "Granite 4.0 Micro", "weighted_score": 8.6, "brief_justification": "The response accurately identifies the connection pool exhaustion issue and provides a comprehensive analysis and actionable solutions. It could be slightly more concise for clarity." }, { "judge_key": "devstral", "judge_name": "Devstral Small", "respondent_key": "qwen3_8b", "respondent_name": "Qwen 3 8B", "weighted_score": 9.6, "brief_justification": "The response accurately identifies the root causes and provides clear, actionable fixes with explanations. It covers all aspects of the issue comprehensively." }, { "judge_key": "devstral", "judge_name": "Devstral Small", "respondent_key": "mistral_nemo", "respondent_name": "Mistral Nemo 12B", "weighted_score": 8.8, "brief_justification": "The response accurately identifies the connection pool exhaustion and timeout issues, provides a comprehensive solution with clear explanations, and offers practical steps to mitigate the problem." }, { "judge_key": "devstral", "judge_name": "Devstral Small", "respondent_key": "llama31_8b", "respondent_name": "Llama 3.1 8B", "weighted_score": 8.6, "brief_justification": "The response accurately identifies the connection pool exhaustion issue and provides a comprehensive fix with clear explanations and additional recommendations." }, { "judge_key": "gemma3_27b", "judge_name": "Gemma 3 27B", "respondent_key": "qwen3_32b", "respondent_name": "Qwen 3 32B", "weighted_score": 8.65, "brief_justification": "The response correctly identifies the connection leak as the root cause and explains the exhaustion pattern well. While the calculation of requests per second a connection can handle is a bit simplistic, the overall explanation is accurate and actionable." }, { "judge_key": "gemma3_27b", "judge_name": "Gemma 3 27B", "respondent_key": "kimi_k25", "respondent_name": "Kimi K2.5", "weighted_score": 9.8, "brief_justification": "The response accurately identifies the connection pool leak as the root cause, provides clear and correct fixes, and thoroughly explains the exhaustion pattern. The additional hardening suggestions are also valuable and practical." }, { "judge_key": "gemma3_27b", "judge_name": "Gemma 3 27B", "respondent_key": "devstral", "respondent_name": "Devstral Small", "weighted_score": 9.4, "brief_justification": "The response accurately identifies the root cause (connection pool exhaustion) and provides a comprehensive solution including code, explanations, and further recommendations. The explanation of the pattern is clear and the code example is well-structured and addresses the issue." }, { "judge_key": "gemma3_27b", "judge_name": "Gemma 3 27B", "respondent_key": "llama4_scout", "respondent_name": "Llama 4 Scout", "weighted_score": 9.8, "brief_justification": "The response accurately identifies the problem, provides a correct and well-explained fix, and thoroughly explains the connection pool exhaustion pattern with mitigation strategies. The additional recommendations are also valuable." }, { "judge_key": "gemma3_27b", "judge_name": "Gemma 3 27B", "respondent_key": "phi4", "respondent_name": "Phi-4 14B", "weighted_score": 9.8, "brief_justification": "The response accurately identifies the root cause (connection pool exhaustion), provides a correct and well-explained fix, and offers valuable additional recommendations for improving the system's resilience. The explanation of the pattern is clear and concise." }, { "judge_key": "gemma3_27b", "judge_name": "Gemma 3 27B", "respondent_key": "granite_40", "respondent_name": "Granite 4.0 Micro", "weighted_score": 9.4, "brief_justification": "The response accurately identifies the problem, explains the connection pool exhaustion pattern clearly, and provides multiple actionable solutions with code examples. It could be slightly more in-depth regarding specific database optimization techniques." }, { "judge_key": "gemma3_27b", "judge_name": "Gemma 3 27B", "respondent_key": "qwen3_8b", "respondent_name": "Qwen 3 8B", "weighted_score": 9.8, "brief_justification": "The response accurately identifies the root cause of the 502 errors, provides a comprehensive fix with code examples, and clearly explains the connection pool exhaustion pattern. The summary table is a nice touch for quick reference." }, { "judge_key": "gemma3_27b", "judge_name": "Gemma 3 27B", "respondent_key": "mistral_nemo", "respondent_name": "Mistral Nemo 12B", "weighted_score": 9.8, "brief_justification": "The response accurately identifies the root cause (connection pool exhaustion and timeouts), provides a comprehensive set of solutions, and clearly explains the underlying pattern. The suggestions are practical and well-explained, covering multiple angles of attack." }, { "judge_key": "gemma3_27b", "judge_name": "Gemma 3 27B", "respondent_key": "llama31_8b", "respondent_name": "Llama 3.1 8B", "weighted_score": 9.2, "brief_justification": "The response accurately identifies the problem, provides a solid fix including code, and explains the connection pool exhaustion pattern well. The additional recommendations and example use case further enhance its practicality and depth." }, { "judge_key": "llama4_scout", "judge_name": "Llama 4 Scout", "respondent_key": "qwen3_32b", "respondent_name": "Qwen 3 32B", "weighted_score": 9.4, "brief_justification": "The response accurately identifies the root cause of the issue as a missing 'client.release()' and provides a clear explanation of the connection pool exhaustion pattern. The breakdown is detailed and actionable." }, { "judge_key": "llama4_scout", "judge_name": "Llama 4 Scout", "respondent_key": "kimi_k25", "respondent_name": "Kimi K2.5", "weighted_score": 9.8, "brief_justification": "The response accurately identifies the connection pool leak issue, provides a clear explanation of the problem and the exhaustion pattern, and offers practical fixes and additional hardening measures." }, { "judge_key": "llama4_scout", "judge_name": "Llama 4 Scout", "respondent_key": "devstral", "respondent_name": "Devstral Small", "weighted_score": 8.6, "brief_justification": "The response accurately identifies the issue as connection pool exhaustion and provides a clear fix by increasing the connection pool size and optimizing database queries. The explanation of the connection pool exhaustion pattern is thorough." }, { "judge_key": "llama4_scout", "judge_name": "Llama 4 Scout", "respondent_key": "gemma3_27b", "respondent_name": "Gemma 3 27B", "weighted_score": 9.8, "brief_justification": "The response accurately identifies the root cause of the issue (connection pool exhaustion) and provides a comprehensive solution, including query optimization, connection pool management, and monitoring. The explanation is clear and detailed, making it highly useful for resolving the problem." }, { "judge_key": "llama4_scout", "judge_name": "Llama 4 Scout", "respondent_key": "phi4", "respondent_name": "Phi-4 14B", "weighted_score": 9.35, "brief_justification": "The response accurately identifies the issue as connection pool exhaustion and provides a clear, actionable fix. It also offers additional recommendations for optimizing the connection pool and handling high traffic loads." }, { "judge_key": "llama4_scout", "judge_name": "Llama 4 Scout", "respondent_key": "granite_40", "respondent_name": "Granite 4.0 Micro", "weighted_score": 9.35, "brief_justification": "The response accurately identifies the issue as connection pool exhaustion and provides a comprehensive analysis and practical solutions to mitigate the problem." }, { "judge_key": "llama4_scout", "judge_name": "Llama 4 Scout", "respondent_key": "qwen3_8b", "respondent_name": "Qwen 3 8B", "weighted_score": 9.6, "brief_justification": "The response accurately identifies the root causes of the 502 errors, provides comprehensive fixes, and explains the connection pool exhaustion pattern. The fixes are actionable and well-explained." }, { "judge_key": "llama4_scout", "judge_name": "Llama 4 Scout", "respondent_key": "mistral_nemo", "respondent_name": "Mistral Nemo 12B", "weighted_score": 8.8, "brief_justification": "The response accurately identifies the problem as connection pool exhaustion and timeouts, provides a clear explanation of the issue, and offers practical solutions to address it. The analysis is thorough, and the suggested fixes are actionable." }, { "judge_key": "llama4_scout", "judge_name": "Llama 4 Scout", "respondent_key": "llama31_8b", "respondent_name": "Llama 3.1 8B", "weighted_score": 8.15, "brief_justification": "The response accurately identifies the problem as connection pool exhaustion and provides a clear fix. However, some details like specific PostgreSQL configuration and advanced monitoring strategies are missing." }, { "judge_key": "phi4", "judge_name": "Phi-4 14B", "respondent_key": "qwen3_32b", "respondent_name": "Qwen 3 32B", "weighted_score": 9.8, "brief_justification": "The response correctly identifies the missing `client.release()` as the root cause of connection pool exhaustion, leading to 502 errors. It provides a clear explanation of the connection pool exhaustion pattern and suggests a practical fix by releasing connections back to the pool after use. The response thoroughly covers the issue and offers actionable insights." }, { "judge_key": "phi4", "judge_name": "Phi-4 14B", "respondent_key": "kimi_k25", "respondent_name": "Kimi K2.5", "weighted_score": 9.8, "brief_justification": "The response accurately diagnoses the connection pool leak and provides clear, actionable solutions. It explains the problem and its causes thoroughly, with practical code examples and additional hardening suggestions." }, { "judge_key": "phi4", "judge_name": "Phi-4 14B", "respondent_key": "devstral", "respondent_name": "Devstral Small", "weighted_score": 9.25, "brief_justification": "The response accurately identifies connection pool exhaustion as the issue and provides a comprehensive solution to address it. It includes code adjustments and infrastructure recommendations, which are clear and actionable. The response could further elaborate on monitoring strategies and potential caching methods for completeness." }, { "judge_key": "phi4", "judge_name": "Phi-4 14B", "respondent_key": "gemma3_27b", "respondent_name": "Gemma 3 27B", "weighted_score": 9.8, "brief_justification": "The response accurately identifies the issue of connection pool exhaustion and provides a comprehensive solution with detailed steps. It covers all aspects of the problem, including query optimization, connection pool management, and monitoring, offering practical and actionable advice." }, { "judge_key": "phi4", "judge_name": "Phi-4 14B", "respondent_key": "llama4_scout", "respondent_name": "Llama 4 Scout", "weighted_score": 9, "brief_justification": "The response accurately identifies the issue of connection pool exhaustion and provides a correct solution with a try-catch-finally block. It covers the problem comprehensively and offers additional recommendations for monitoring and optimization. The explanation is clear and structured, with insightful analysis on connection pool patterns." }, { "judge_key": "phi4", "judge_name": "Phi-4 14B", "respondent_key": "granite_40", "respondent_name": "Granite 4.0 Micro", "weighted_score": 9.2, "brief_justification": "The response accurately identifies connection pool exhaustion as the issue and provides a comprehensive set of solutions. It is clear and well-structured, offering practical advice with depth in analysis. The score is slightly less than perfect due to not exploring all possible causes for the errors." }, { "judge_key": "phi4", "judge_name": "Phi-4 14B", "respondent_key": "qwen3_8b", "respondent_name": "Qwen 3 8B", "weighted_score": 10, "brief_justification": "The response accurately diagnoses the root causes of the 502 errors, provides comprehensive fixes, and explains the connection pool exhaustion pattern in detail. It is clear, well-structured, and offers practical value with actionable steps." }, { "judge_key": "phi4", "judge_name": "Phi-4 14B", "respondent_key": "mistral_nemo", "respondent_name": "Mistral Nemo 12B", "weighted_score": 9.4, "brief_justification": "The response accurately identifies the issues of connection pool exhaustion and timeouts, providing effective solutions such as increasing pool size, adjusting Nginx timeouts, optimizing database queries, and implementing caching. The explanation of the connection pool exhaustion pattern is insightful and practical, offering a clear understanding of the problem and its feedback loop." }, { "judge_key": "phi4", "judge_name": "Phi-4 14B", "respondent_key": "llama31_8b", "respondent_name": "Llama 3.1 8B", "weighted_score": 8.6, "brief_justification": "The response correctly identifies connection pool exhaustion as the cause of the 502 errors and provides a detailed fix by increasing the pool size and implementing connection reuse. It also suggests monitoring and additional tools for managing connections, which is practical and actionable. However, it could further elaborate on the connection pool configuration and potential database optimizations." }, { "judge_key": "granite_40", "judge_name": "Granite 4.0 Micro", "respondent_key": "qwen3_32b", "respondent_name": "Qwen 3 32B", "weighted_score": 8.4, "brief_justification": "The response accurately identifies the root cause of connection pool exhaustion due to missing client release, provides a clear fix, and explains the pattern well, though it could delve deeper into connection timeout implications." }, { "judge_key": "granite_40", "judge_name": "Granite 4.0 Micro", "respondent_key": "kimi_k25", "respondent_name": "Kimi K2.5", "weighted_score": 8.8, "brief_justification": "The response accurately identifies the connection pool exhaustion issue, provides a clear fix using pool.query() or explicit release, explains the exhaustion pattern well, and adds useful hardening suggestions." }, { "judge_key": "granite_40", "judge_name": "Granite 4.0 Micro", "respondent_key": "devstral", "respondent_name": "Devstral Small", "weighted_score": 8.8, "brief_justification": "The response accurately identifies connection pool exhaustion as the cause of 502 errors, provides a clear explanation of the pattern, offers specific fixes including increasing the pool size and optimizing queries, and includes practical recommendations for monitoring and scaling." }, { "judge_key": "granite_40", "judge_name": "Granite 4.0 Micro", "respondent_key": "gemma3_27b", "respondent_name": "Gemma 3 27B", "weighted_score": 8.8, "brief_justification": "The response accurately diagnoses connection pool exhaustion and slow query execution, provides a comprehensive fix including query optimization, pool size adjustment, and monitoring, and explains the underlying pattern well." }, { "judge_key": "granite_40", "judge_name": "Granite 4.0 Micro", "respondent_key": "llama4_scout", "respondent_name": "Llama 4 Scout", "weighted_score": 8.8, "brief_justification": "The response accurately identifies the connection pool exhaustion issue, provides a clear fix, and explains the underlying pattern well, though it could delve slightly deeper into optimization strategies." }, { "judge_key": "granite_40", "judge_name": "Granite 4.0 Micro", "respondent_key": "phi4", "respondent_name": "Phi-4 14B", "weighted_score": 8.8, "brief_justification": "The response accurately identifies connection pool exhaustion as the cause of 502 errors, provides a clear fix for releasing connections, and explains the underlying pattern well, though it could delve deeper into optimization strategies." }, { "judge_key": "granite_40", "judge_name": "Granite 4.0 Micro", "respondent_key": "qwen3_8b", "respondent_name": "Qwen 3 8B", "weighted_score": 8.8, "brief_justification": "The response accurately identifies connection pool exhaustion and PostgreSQL limits as root causes, provides comprehensive fixes, and explains the underlying pattern effectively." }, { "judge_key": "granite_40", "judge_name": "Granite 4.0 Micro", "respondent_key": "mistral_nemo", "respondent_name": "Mistral Nemo 12B", "weighted_score": 8.8, "brief_justification": "The response accurately identifies the connection pool exhaustion and timeout issues, provides relevant fixes, and explains the underlying pattern well, though it could delve deeper into specific optimization techniques." }, { "judge_key": "granite_40", "judge_name": "Granite 4.0 Micro", "respondent_key": "llama31_8b", "respondent_name": "Llama 3.1 8B", "weighted_score": 8.4, "brief_justification": "The response accurately identifies connection pool exhaustion as the root cause, provides a clear fix, and explains the underlying pattern well, though it could delve deeper into alternative solutions like query optimization." }, { "judge_key": "qwen3_8b", "judge_name": "Qwen 3 8B", "respondent_key": "qwen3_32b", "respondent_name": "Qwen 3 32B", "weighted_score": 7.85, "brief_justification": "Correctly identifies the missing client.release() as the root cause, but could elaborate more on Nginx timeout settings and query optimization opportunities. The explanation is clear but lacks some depth in scalability solutions." }, { "judge_key": "qwen3_8b", "judge_name": "Qwen 3 8B", "respondent_key": "kimi_k25", "respondent_name": "Kimi K2.5", "weighted_score": 10, "brief_justification": "The response accurately identifies the connection pool leak, explains the exhaustion pattern, provides actionable fixes, and includes practical hardening techniques. It thoroughly addresses all aspects of the problem with clear examples and logical flow." }, { "judge_key": "qwen3_8b", "judge_name": "Qwen 3 8B", "respondent_key": "devstral", "respondent_name": "Devstral Small", "weighted_score": 8.8, "brief_justification": "The response correctly identifies connection pool exhaustion as the root cause and provides actionable fixes. It covers key aspects but could have more deeply analyzed the load calculation and potential Nginx/Node.js factors." }, { "judge_key": "qwen3_8b", "judge_name": "Qwen 3 8B", "respondent_key": "gemma3_27b", "respondent_name": "Gemma 3 27B", "weighted_score": 9.6, "brief_justification": "The response accurately explains connection pool exhaustion and slow query issues, provides actionable fixes, and covers all aspects of the problem with clear examples and troubleshooting steps." }, { "judge_key": "qwen3_8b", "judge_name": "Qwen 3 8B", "respondent_key": "llama4_scout", "respondent_name": "Llama 4 Scout", "weighted_score": 9.4, "brief_justification": "The response accurately identifies connection pool exhaustion as the root cause and provides a correct fix. It explains the pattern thoroughly but misses addressing the 'connect ETIMEDOUT' error, which could be a separate issue. The solution is actionable and includes practical recommendations." }, { "judge_key": "qwen3_8b", "judge_name": "Qwen 3 8B", "respondent_key": "phi4", "respondent_name": "Phi-4 14B", "weighted_score": 10, "brief_justification": "The response accurately identifies connection pool exhaustion as the root cause, provides a clear fix with code examples, explains the pattern thoroughly, and offers actionable recommendations. All criteria are met with high precision and practical value." }, { "judge_key": "qwen3_8b", "judge_name": "Qwen 3 8B", "respondent_key": "granite_40", "respondent_name": "Granite 4.0 Micro", "weighted_score": 10, "brief_justification": "The response accurately identifies connection pool exhaustion as the root cause, explains the pattern thoroughly, and provides actionable fixes covering pool sizing, best practices, and scaling strategies. All criteria are met with excellent precision and practical value." }, { "judge_key": "qwen3_8b", "judge_name": "Qwen 3 8B", "respondent_key": "mistral_nemo", "respondent_name": "Mistral Nemo 12B", "weighted_score": 9.4, "brief_justification": "The response accurately identifies connection pool exhaustion and timeout causes, provides actionable fixes, and explains the pattern thoroughly. It covers all technical aspects but could have explicitly linked the 200 req/s threshold to pool sizing decisions." }, { "judge_key": "qwen3_8b", "judge_name": "Qwen 3 8B", "respondent_key": "llama31_8b", "respondent_name": "Llama 3.1 8B", "weighted_score": 9, "brief_justification": "The response accurately identifies connection pool exhaustion as the root cause and provides a valid fix. It covers key aspects but could have deeper analysis on calculating optimal pool size. The code and recommendations are practical and actionable." }, { "judge_key": "mistral_nemo", "judge_name": "Mistral Nemo 12B", "respondent_key": "qwen3_32b", "respondent_name": "Qwen 3 32B", "weighted_score": 8.25, "brief_justification": "The response accurately identifies the missing `client.release()` as the root cause, explains the connection leak, and outlines the pool exhaustion pattern. It could have provided more detail on how to fix the issue (e.g., adding `client.release()`) and the expected improvement after the fix." }, { "judge_key": "mistral_nemo", "judge_name": "Mistral Nemo 12B", "respondent_key": "kimi_k25", "respondent_name": "Kimi K2.5", "weighted_score": 8.8, "brief_justification": "The response accurately diagnoses the issue as a connection pool leak and provides clear, actionable fixes. It also explains the exhaustion pattern and suggests additional hardening measures." }, { "judge_key": "mistral_nemo", "judge_name": "Mistral Nemo 12B", "respondent_key": "devstral", "respondent_name": "Devstral Small", "weighted_score": 8.2, "brief_justification": "The response accurately diagnoses the issue and provides a comprehensive solution. It could have delved deeper into optimizing database queries and caching strategies, hence the slight reduction in depth score." }, { "judge_key": "mistral_nemo", "judge_name": "Mistral Nemo 12B", "respondent_key": "gemma3_27b", "respondent_name": "Gemma 3 27B", "weighted_score": 8.8, "brief_justification": "The response accurately diagnoses the issue, provides a comprehensive fix, and explains the connection pool exhaustion pattern in detail. It's clear, insightful, and actionable, with the only minor deduction in clarity due to the length of the response." }, { "judge_key": "mistral_nemo", "judge_name": "Mistral Nemo 12B", "respondent_key": "llama4_scout", "respondent_name": "Llama 4 Scout", "weighted_score": 8.05, "brief_justification": "The response accurately diagnoses the issue, provides a clear fix, and offers useful explanations and recommendations. However, it could delve deeper into potential optimizations and provide more specific guidance on rate limiting." }, { "judge_key": "mistral_nemo", "judge_name": "Mistral Nemo 12B", "respondent_key": "phi4", "respondent_name": "Phi-4 14B", "weighted_score": 8.15, "brief_justification": "The response accurately diagnoses the issue, provides a clear fix, and offers useful insights into connection pool management. It could have provided more information on how to monitor and optimize the connection pool size and settings." }, { "judge_key": "mistral_nemo", "judge_name": "Mistral Nemo 12B", "respondent_key": "granite_40", "respondent_name": "Granite 4.0 Micro", "weighted_score": 8.05, "brief_justification": "The response accurately diagnoses the issue and provides comprehensive solutions. However, some aspects could be clearer and more concise." }, { "judge_key": "mistral_nemo", "judge_name": "Mistral Nemo 12B", "respondent_key": "qwen3_8b", "respondent_name": "Qwen 3 8B", "weighted_score": 9.4, "brief_justification": "The response accurately diagnoses the issue, provides clear fixes, explains the underlying patterns, and offers practical solutions. It's highly useful and well-structured." }, { "judge_key": "mistral_nemo", "judge_name": "Mistral Nemo 12B", "respondent_key": "llama31_8b", "respondent_name": "Llama 3.1 8B", "weighted_score": 8.05, "brief_justification": "The response accurately identifies connection pool exhaustion as the root cause, provides a comprehensive fix, and offers relevant recommendations. However, it could delve deeper into the connection pool exhaustion pattern and provide more specific guidance on monitoring and adjusting parameters." }, { "judge_key": "llama31_8b", "judge_name": "Llama 3.1 8B", "respondent_key": "qwen3_32b", "respondent_name": "Qwen 3 32B", "weighted_score": 8.8, "brief_justification": "The response accurately identifies the root cause of the issue, explains the connection pool exhaustion pattern, and provides a clear fix, but could delve deeper into the implications of connection pooling and potential optimizations." }, { "judge_key": "llama31_8b", "judge_name": "Llama 3.1 8B", "respondent_key": "kimi_k25", "respondent_name": "Kimi K2.5", "weighted_score": 9.6, "brief_justification": "The response accurately diagnoses the connection pool exhaustion issue, provides two fixes, and offers a detailed explanation of the exhaustion pattern, including a key insight about the 'too many clients' error being a red herring." }, { "judge_key": "llama31_8b", "judge_name": "Llama 3.1 8B", "respondent_key": "devstral", "respondent_name": "Devstral Small", "weighted_score": 9.05, "brief_justification": "The response accurately identifies the connection pool exhaustion pattern, provides a clear explanation, and offers actionable steps to fix the issue, but could benefit from more detailed information on how to optimize database queries and implement caching strategies." }, { "judge_key": "llama31_8b", "judge_name": "Llama 3.1 8B", "respondent_key": "gemma3_27b", "respondent_name": "Gemma 3 27B", "weighted_score": 9.6, "brief_justification": "The response provides a thorough diagnosis of the issue, explains the connection pool exhaustion pattern, and offers a multi-pronged solution with clear steps and code examples. The explanation is detailed and easy to follow, making it highly useful for resolving the problem." }, { "judge_key": "llama31_8b", "judge_name": "Llama 3.1 8B", "respondent_key": "llama4_scout", "respondent_name": "Llama 4 Scout", "weighted_score": 9.45, "brief_justification": "The response accurately diagnoses the connection pool exhaustion pattern, provides a clear fix, and offers actionable recommendations for mitigation and optimization." }, { "judge_key": "llama31_8b", "judge_name": "Llama 3.1 8B", "respondent_key": "phi4", "respondent_name": "Phi-4 14B", "weighted_score": 9.05, "brief_justification": "The response accurately diagnoses the connection pool exhaustion issue, provides a clear explanation, and offers actionable fixes and recommendations to improve the system's performance and scalability." }, { "judge_key": "llama31_8b", "judge_name": "Llama 3.1 8B", "respondent_key": "granite_40", "respondent_name": "Granite 4.0 Micro", "weighted_score": 8.6, "brief_justification": "The response accurately identifies the issue, provides a clear explanation of the connection pool exhaustion pattern, and offers actionable steps for resolution." }, { "judge_key": "llama31_8b", "judge_name": "Llama 3.1 8B", "respondent_key": "qwen3_8b", "respondent_name": "Qwen 3 8B", "weighted_score": 8.8, "brief_justification": "The response accurately identifies the root causes of the 502 errors, provides actionable fixes, and explains the connection pool exhaustion pattern in detail." }, { "judge_key": "llama31_8b", "judge_name": "Llama 3.1 8B", "respondent_key": "mistral_nemo", "respondent_name": "Mistral Nemo 12B", "weighted_score": 9.05, "brief_justification": "The response accurately identifies the issue, provides a detailed explanation, and offers actionable solutions to improve the API's performance under high load." } ], "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)" } }