| name | production-quality |
| description | This skill should be used when preparing code for production, running "mix precommit", "mix compile --warnings-as-errors", "mix credo --strict", "mix format", "mix test", adding typespecs, evaluating security posture, checking migration safety, or reviewing code before committing |
Production Quality
Overview
Production readiness is an escalation ladder — L0 (compiles) through L7 (documented). Most features should reach at least L3 before merge.
Escalation Ladder
| Level | Gate | Command/Check |
|---|
| L0 | Compiles cleanly | mix compile --warnings-as-errors (includes set-theoretic type checks on 1.18+) |
| L1 | Formatted | mix format (with Styler) |
| L2 | Static analysis | mix credo --strict |
| L3 | Tested | mix test — all ok/error paths, edge cases |
| L4 | Typed | @spec on every public function, concrete types (compiler infers many types on 1.18+, specs remain valuable for API documentation) |
| L5 | Secure | OWASP defenses: parameterized queries, escaped output, changeset validation |
| L6 | Observable | Telemetry on all 4 layers (OS/VM, framework, app, user) |
| L7 | Documented | @moduledoc, @doc with examples, "why" comments |
Precommit gate (L0-L3 automated):
# mix.exs aliases
precommit: ["compile --warnings-as-errors", "deps.unlock --unused", "format", "credo --strict", "test"]
Common Mistakes
- Skipping L2 (static analysis): Credo catches naming issues, long functions, and anti-patterns that code review misses
- Treating L6 (observability) as optional: You can't fix what you can't see — add telemetry before production, not after the first incident
- Unsafe migrations: Adding indexes or changing column types without
concurrently: true or multi-step deployment causes downtime
- Silent error handling: 92% of catastrophic failures come from incorrect error handling — test every
{:error, _} branch
- Zombie metrics: Metrics nobody acts on are waste. If it can't drive a decision, delete it
Reference Files
Read the file that matches your current problem:
escalation-ladder.md — When: Need details on any production readiness level (L0-L7). Full Production Readiness Ladder (L0-L7 with code examples, gate criteria)testing.md — When: Designing test strategy or setting up TDD workflow. Testing strategy, TDD, error handling imperative, documentation standardsproperty-based-testing.md — When: Testing with StreamData generators or properties. StreamData generators, custom generators, property patterns (roundtrip, idempotency, oracle, metamorphic), shrinking, Ecto integrationsecurity.md — When: Hardening against injection, XSS, CSRF, or managing secrets. SQL injection, XSS, CSRF, input validation, secrets management, timing attacks, magic link authobservability.md — When: Adding telemetry, tracing, or alerting. Telemetry layers, span conventions, tracing-as-analytics, alerting, gray failures, degraded mode, process labelsdatabase.md — When: Writing migrations or tuning Ecto queries. Safe Ecto migrations, isolation level warnings, dependency SLAs, performance guidelinesecto-preloading.md — When: Fixing N+1 queries or choosing preload strategy. N+1 detection and prevention, preload strategies (join, subquery, inline), LiveView preloadingerror-handling.md — When: Designing error flows or debugging crash patterns. Crash early patterns, strict-then-loosen, complexity analysisdeployment.md — When: Building releases, health checks, or Docker configs. Mix releases, health checks (liveness/readiness), graceful shutdown, Docker, Fly.io/K8s patternsconfiguration.md — When: Choosing between compile-time and runtime config. config.exs vs runtime.exs, compile_env vs get_env, runtime secrets, config providers
Commands
/precommit — Enforces L0-L3 automatically (compile, format, credo, test)/review [file] — Comprehensive review against L4-L7 standards/spike-migrate — Upgrade SPIKE code to production quality
Related Skills
- elixir-patterns: GenServer, Supervisor, OTP patterns
- cognitive-complexity: Ousterhout principles, deep modules, reducing complexity
- performance-analyzer: Benchmarking, profiling, latency analysis
- enforcing-precommit: Iron law enforcement for precommit before commits
