SlotWise
Studies in this cluster, in series order. Each one keeps its own URL.
High-level design
HLD interview and machine-coding scale-up: capacity, APIs, data model, caching, sharding, and the path from a single-node solution to production.
SlotWise
3 studies- 1.SlotWise Reservation Service Incident - HLD Debug & Fix PathA reservation service starts double-booking slots under load. Reproduce, trace isolation and locking choices, fix with the right transaction boundaries, and ship a regression test.
- 2.SlotWise - SQLAlchemy Transaction Fix & TestsPartial unique index on active reservations, a transactional reserve that maps IntegrityError to 409, optional SELECT FOR UPDATE on the slot row, and a regression test that spawns concurrent reservers.
- 3.SlotWise - Load Repro & Isolation Decision ChartHow to reproduce the double-book under load, which isolation level still loses without a constraint, and a decision chart for constraint versus row lock versus serializable retries.