Backend & distributed systems

Background job and queue testing: 8 skills (bullmq-tests, celery-tests, cron-job-test-author, idempotency-test-author, kafka-consumer-tests, rabbitmq-tests, sidekiq-tests, sqs-tests) and 1 agent (async-job-health-critic). Covers async job runners, queue patterns, scheduled jobs, and idempotency guarantees.

Cache testing across layers: Redis cache patterns, CDN cache-purge testing (Cloudflare, Fastly, CloudFront), Varnish VTC syntax, browser Cache-Control tests, cache-coherence + stampede + stale-while-revalidate references, and a cache-key collision detector. Covers RFC 9111 HTTP caching and the canonical multi-tier cache discipline (browser to CDN to app to data store).

Concurrency + race-condition testing: 6 skills (async-ordering-tests, deadlock-detection-harness, go-race-detector-workflow, jepsen-patterns, mvcc-isolation-tests, race-condition-test-author) and 1 agent (concurrency-critic). Code-level data races, distinct from qa-chaos (infrastructure fault injection).

Database migration testing: 4 skills (atlas-migrations, flyway-migrations, liquibase-migrations, sqlmesh-migrations) and 2 agents (db-migration-performance-critic, migration-blast-radius-reviewer). Covers schema-change safety, blast-radius review, and rollback verification across the major migration tools.

Distributed tracing assertion testing: 6 skills (jaeger-trace-tests, opentelemetry-trace-assertions, otel-collector-config-tester, tempo-trace-tests, trace-spec-author, zipkin-trace-tests) and 1 agent (trace-coverage-reviewer). Asserts on production trace shape (spans, attributes, parent links, status), not just on aggregate metrics.

Saga + CQRS + event sourcing test patterns: 5 skills (cqrs-projection-tests, event-sourcing-tests, eventual-consistency-tests, outbox-pattern-test-author, saga-transaction-tests) and 1 agent (saga-critic). Covers ACD-without-isolation saga tests, replay determinism, and projection consistency windows.

Serverless platform testing: AWS SAM Local, .NET Lambda Test Tools, Cloudflare Workers Miniflare, Vercel Edge Runtime, Netlify Functions, Serverless Framework, plus cold-start + timeout budget references and a serverless integration-test builder. Covers Lambda / Workers / Edge runtimes which have specific testing patterns (cold-start budgets, timeout testing, local emulators, edge-runtime divergence) absent from generic web-server test plugins.

Time-related testing: fake-clock libraries (libfaketime, sinon-fake-timers, jest-fake-timers, freezegun, timecop, mockclock), DST + leap-second references, ISO-8601 vs RFC 3339 reference, and a timezone test matrix builder. Covers time-based bugs (DST transitions, leap seconds, timezone arithmetic, clock skew) which are high-incident-rate but specific tooling is scattered.