performance

Performance Review

Target

$ARGUMENTS

Context Gathering

Before starting, scan the project to understand its tech stack and entry points:

• Run: !find . -maxdepth 2 -name "package.json" -o -name "pom.xml" -o -name "build.gradle" -o -name "requirements.txt" -o -name "go.mod" -o -name "Cargo.toml" 2>/dev/null | head -10
• Run: !find . -maxdepth 3 -name "*.config.*" -o -name "*.conf" 2>/dev/null | grep -v node_modules | head -10

If $ARGUMENTS is provided, focus only on that path. Otherwise, analyze the full project.

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Performance Review Checklist

Perform a deep analysis covering ALL of the following categories. For each finding, include:

• 📍 Location: file + line number(s)
• 🔴 Severity: Critical / High / Medium / Low
• 💡 Recommendation: concrete fix with code example when possible

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1. 🔁 Algorithm & Complexity

• Identify O(n²) or worse loops (nested iterations over large collections)
• Find linear scans that could use maps/sets/indexes
• Spot redundant or repeated computations inside loops
• Check recursive functions for missing memoization or infinite-loop risk

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2. 🗄️ Database & I/O

• Look for N+1 query patterns (queries inside loops)
• Find missing pagination on large result sets
• Check for missing indexes (look at WHERE/JOIN/ORDER BY clauses in raw queries or ORM calls)
• Detect synchronous I/O blocking the main thread (Node.js, Python async, etc.)
• Identify missing connection pooling or connection leaks
• Spot unnecessary SELECT * when only specific fields are needed

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3. 💾 Memory Management

• Find memory leaks: event listeners added but never removed, unclosed streams, growing caches without eviction
• Detect large objects or arrays being kept in memory longer than needed
• Identify cloning/copying of large data structures unnecessarily
• Check for string concatenation in loops (should use builders/join)

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4. ⚡ Caching Opportunities

• Find repeated identical computations or DB/API calls with the same input
• Check if HTTP responses set proper cache headers
• Spot missing memoization on pure/expensive functions
• Identify opportunities for Redis/in-memory cache on hot paths

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5. 🌐 Network & API

• Detect sequential await chains that could be parallelized (Promise.all, goroutines, asyncio.gather, etc.)
• Find uncompressed API payloads (missing gzip/brotli)
• Identify missing HTTP/2 or keep-alive usage
• Spot excessive or redundant external API calls
• Check for missing request timeouts and retry strategies

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6. 🖼️ Frontend Performance (if applicable)

• Check for render-blocking resources (undeferred scripts/styles)
• Find large unoptimized images (missing lazy loading, wrong formats)
• Detect unnecessary re-renders (missing React.memo, useMemo, useCallback)
• Spot large bundle sizes (imports of entire libraries when only a piece is needed)
• Identify layout thrashing (forced synchronous layouts in JS)

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7. 🏗️ Infrastructure & Build

• Find unminified or uncompressed production assets
• Detect missing CDN usage for static assets
• Identify missing code splitting or lazy loading
• Check for disabled HTTP cache headers in production configs

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Output Format

Produce the report in this exact structure:

## 🚀 Performance Review Report
**Target:** [file/module/project]
**Date:** [today]
**Stack detected:** [detected tech stack]

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### Executive Summary
[2–3 sentence overview of overall performance health]

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### 🔴 Critical Issues ([count])
[List each with location, description, and recommended fix]

### 🟠 High Priority ([count])
[List each with location, description, and recommended fix]

### 🟡 Medium Priority ([count])
[List each with location, description, and recommended fix]

### 🟢 Low / Nice-to-Have ([count])
[List each with location, description, and recommended fix]

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### Quick Wins (can be fixed in < 30 min)
[Bullet list of the fastest, lowest-risk improvements]

### Estimated Impact
[For the top 3 findings, estimate the expected improvement in latency / throughput / memory]

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### Next Steps
1. [Prioritized action item]
2. [Prioritized action item]
3. [Prioritized action item]