Backend Skills

Keep API docs in sync with implementation by generating or validating OpenAPI/Swagger specs, detecting undocumented routes, and fixing spec drift. Use when the user asks to generate docs, validate a spec, find undocumented endpoints, or update stale API documentation.

Implement API versioning with URL or header strategies, deprecation handling, and backward compatibility. Use when the user asks about versioning, managing breaking changes, evolving APIs, supporting multiple versions, or handling v1/v2 migrations.

Implement cache invalidation strategies for data consistency. Use when handling stale data, invalidating on updates, designing cache flows, or working with SWR, cache tags, or event-driven invalidation across Redis, CDNs, or client caches.

Implement correct transaction handling with proper isolation levels, retries, and rollback on failure. Use when dealing with concurrency issues, deadlocks, inconsistent data, or transaction design (e.g., SELECT FOR UPDATE, locking strategies).

Implement JWT auth on the backend, including token generation, validation, refresh rotation, revocation, and secure storage. Use when building token-based auth, securing endpoints, or handling expiry and access/refresh flows.

Implement safe database migrations with zero-downtime patterns, rollbacks, and strategies for large schema changes without data loss. Use when the user asks about migrations, schema updates, backfills, column/table changes, or tools like Flyway, Liquibase, Alembic, or ActiveRecord.

Detect and fix N+1 query patterns using eager loading, batching, or dataloader approaches. Use when queries run in loops, ORM lazy loading causes repeated DB calls, or the user reports slow endpoints or N+1 issues. Also trigger when the user shares code with loops that call .find(), .load(), .fetch(), or any ORM relation access inside an iteration, or when query logs show the same query repeated with different IDs.

Implement efficient pagination using offset, cursor, or keyset strategies. Use when fixing slow or deep pagination, high offsets, infinite scroll, or designing list endpoints.

Optimize slow SQL queries using plan analysis, indexing, join tuning, subquery/CTE simplification, and pagination improvements. Use when the user shares slow queries, EXPLAIN output, or reports high execution time, sequential scans, or inefficient joins.

Build a production-grade outbound webhook system with retries, signing, failure tracking, and re-delivery. Use when implementing webhook delivery, event subscriptions, or handling webhook failures and reliability.