- name
- elixir-performance-review
- description
- Reviews Elixir code for performance issues including GenServer bottlenecks, memory usage, and concurrency patterns. Use when reviewing high-throughput code or investigating performance issues.
Elixir Performance Review
Quick Reference
| Issue Type | Reference |
|---|---|
| Mailbox overflow, blocking calls | references/genserver-bottlenecks.md |
| When to use ETS, read/write concurrency | references/ets-patterns.md |
| Binary handling, large messages | references/memory.md |
| Task patterns, flow control | references/concurrency.md |
Review Checklist
GenServer
- [ ] Not a single-process bottleneck for all requests
- [ ] No blocking operations in handle_call/cast
- [ ] Proper timeout configuration
- [ ] Consider ETS for read-heavy state
Memory
- [ ] Large binaries not copied between processes
- [ ] Streams used for large data transformations
- [ ] No unbounded data accumulation
Concurrency
- [ ] Task.Supervisor for dynamic tasks (not raw Task.async)
- [ ] No unbounded process spawning
- [ ] Proper backpressure for message producers
Database
- [ ] Preloading to avoid N+1 queries
- [ ] Pagination for large result sets
- [ ] Indexes for frequent queries
Valid Patterns (Do NOT Flag)
- Single GenServer for low-throughput - Not all state needs horizontal scaling
- Synchronous calls for critical paths - Consistency may require it
- In-memory state without ETS - ETS has overhead for small state
- Enum over Stream for small collections - Stream overhead not worth it
Context-Sensitive Rules
| Issue | Flag ONLY IF |
|---|---|
| GenServer bottleneck | Handles > 1000 req/sec OR blocking I/O in callbacks |
| Use streams | Processing > 10k items OR reading large files |
| Use ETS | Read:write ratio > 10:1 AND concurrent access |
Gates — before reporting
Do these in order for the performance review. Do not publish findings until each step passes.
- Protocol loaded — Read review-verification-protocol and apply its checks for each finding (hot paths, concurrency, resource use). Pass: For every substantive finding, you can name which protocol subsection you satisfied or state N/A with reason (e.g. pure reference to this skill’s Valid Patterns).
- Anchored evidence — Pass: Each finding includes a concrete locator:
path:line(or line range), orModule.function/arityplus a short quoted snippet from the file. - Performance claims — For anything under Context-Sensitive Rules, or any claim of bottleneck, N+1, unbounded growth, or heavy memory/binary cost, Pass: You state the observed or measured fact that meets “Flag ONLY IF” (e.g. rate, item count, ratio), or attach an artifact (profiler output, SQL/log excerpt,
grep/search scope)—otherwise downgrade to question / suspected with what was not verified.
Before Submitting Findings
Complete Gates — before reporting (section above) first; the verification protocol is mandatory input to those gates.