performance

name: performance description: Performance optimization and bottleneck detection. Identifies N+1 queries, memory leaks, async issues, and caching opportunities. Use when investigating slow operations, optimizing response times, or detecting performance issues.

Performance

Systematic analysis focusing on queries, memory, async patterns, and caching.

When to Use

• N+1 query detection
• Memory leak investigation
• Response time optimization
• Caching strategy design
• Async code review

MCP Workflow

# 1. Search for anti-patterns
serena.search_for_pattern(
  "for.*in.*find|map.*repository",
  restrict_search_to_code_files=True
)

# 2. Analyze suspicious method
serena.find_symbol("SlowService/method", include_body=True)

# 3. Trace hot paths
serena.find_referencing_symbols("FrequentlyCalledMethod")

# 4. Past optimizations
claude-mem.search(query="performance", project="<project>")

# 5. Framework patterns
context7.get-library-docs("<framework>", topic="performance")

Common Issues

N+1 Queries

PROBLEM:
for item in collection:
    fetch related_data(item.id)  # N queries

SOLUTION:
ids = collection.map(item => item.id)
all_data = fetch_all_by_ids(ids)  # 1 query
lookup = create_map(all_data)

Missing Pagination

PROBLEM: fetch_all()  # No limit

SOLUTION: fetch_paginated(page, size)

Missing Caching

PROBLEM: get_user(id)  # Called repeatedly

SOLUTION:
@cacheable(key="user:{id}", ttl=300)
get_user(id)

Blocking in Async

PROBLEM:
async function process():
    result = sync_blocking_call()

SOLUTION:
async function process():
    result = await async_call()

Memory Leaks

PROBLEM:
global_cache.add(item)  # Never removed

SOLUTION:
cache = LRUCache(max_size=1000)

Detection Patterns

# N+1 - queries in loops
serena.search_for_pattern("for.*find|map.*query|loop.*fetch")

# Unbounded fetches
serena.search_for_pattern("findAll|SELECT.*FROM.*(?!.*LIMIT)")

# Blocking in async
serena.search_for_pattern("block|wait|sleep.*async")

# Memory leaks
serena.search_for_pattern("static.*list|global.*cache")

Output Format

## Performance: [Scope]

### Metrics
| Metric | Current | Target |
|--------|---------|--------|
| p95 Latency | 500ms | <200ms |
| Throughput | 100 rps | 500 rps |

### Issues

#### 1. [Title]
**Severity:** High / Medium / Low
**Location:** `file:line`
**Type:** N+1 / Memory / Blocking

**Problem:** [description]
**Impact:** [quantified]
**Fix:** [solution]
**Improvement:** [estimate]

### Recommendations
1. **[High]** Fix N+1 queries
2. **[Medium]** Add caching

Caching Strategies

Patterns

# Read-through
get(key): cache.get(key) or (fetch + cache.set)

# Write-through
set(key, value): cache.set + source.save

# Invalidation
on_update(entity): cache.invalidate(entity.key)

Database Optimization

# Select only needed columns
SELECT id, name FROM users  # Not SELECT *

# Add indexes
CREATE INDEX idx_users_email ON users(email)

# Use EXPLAIN
EXPLAIN SELECT ...

# Limit results
SELECT ... LIMIT 100

# Use joins
SELECT u.*, o.* FROM users u
JOIN orders o ON u.id = o.user_id

Checklist

Database

• No N+1 queries
• Pagination on lists
• Indexes on queried columns

Memory

• No growing static collections
• Resources properly closed
• Cache has eviction policy

Async

• No blocking in async
• Timeouts on external calls
• Backpressure handling