Mechanism Labs
One place per mechanism: code the toy and watch it run → see how it evolves to production (ShedLock, Redis, Hi/Lo, …) → explain it in English out loud against the gold answer. Each lab is one of your résumé bullets.
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- Cache Stampede: One Compute, Many Callerscache-stampedecaching · concurrency · single-flight · thundering-herd · java
- Circuit Breaker: Fail Fast on a Dead Dependencycircuit-breakercircuit-breaker · resilience · state-machine · fault-tolerance
- Dead-Letter Queue: bound retries, don't loop foreverdead-letter-queuedead-letter-queue · retries · message-queue · backpressure · java
- Distributed lock: one nightly job, two servers (ShedLock)distributed-lockSK AX — eliminated cross-server duplicate execution of a scheduled job with a distributed lock (ShedLock / job_lock table).
- Idempotency store: a retried charge must not double-applyidempotency-keySK AX — staging-table + batch-worker dedup keyed on a request key, cutting ~20 monthly reprocessing/double-apply cases to ~0.
- Offer state machine: status is a business eventstate-machineOpendoor's offer lifecycle = status-change-as-business-event with validation + audit — the same transaction-integrity shape as the manufacturing/financial state work at SK AX.
- Optimistic lock: two editors, one offer, one versionoptimistic-lockGuarded concurrent edits to the same offer with a version column (compare-and-set) so a stale write is rejected instead of silently clobbering the winning update.
- Outbox: don't dual-writeoutboxoutbox · dual-write · at-least-once · consistency · distributed-systems
- Queue Worker: Ack After Processingqueue-workerqueue · at-least-once · concurrency · idempotency
- Race Condition: Lost Update on a Shared Counterrace-conditionconcurrency · race-condition · compare-and-set · atomicity · java
- Rate Limiter: Token Bucketrate-limiterrate-limiter · token-bucket · concurrency · java
- Retry storm: cap attempts + exponential backoffretry-backoffconcurrency · retry · backoff · resilience · opendoor
- Row-level lock: the multi-instance ID generatorpessimistic-lockSK AX — resolved duplicate ID generation across multi-instance manufacturing execution services with Oracle row-level locks (FOR UPDATE).
- Saga compensation: undo completed steps on failuresagasaga · compensation · distributed-transactions · rollback · java
- Task board state machine: a status is earned, not setstate-machineAn ops task board is the same transaction-integrity shape as Opendoor's offer lifecycle and the manufacturing/financial state work at SK AX — status-change-as-business-event with validation + audit.