Design a Shift Scheduling System

Clarified who creates schedules (manual vs auto-generated) and whether compliance/labor-law rules are in scope
Established functional scope: shift CRUD, publish lifecycle, swap/pick-up, notifications, availability
Defined non-functional targets: consistency for assignment, latency for reads, scale (employees/locations/shifts)

Proposed distinct services (Scheduling, Availability, Swap, Notification) rather than one monolith
Chose relational store for shifts to support transactional/locking guarantees, with rationale vs NoSQL
Included a caching layer for hot schedule reads and an event backbone (queue/Kafka) for notifications/audit
Designed sensible schema/indexes supporting both "schedule by location" and "schedule by employee" access patterns

Addressed conflict/double-booking prevention with a concrete mechanism (sync check, locking/versioning)
Addressed publish as a bulk/async operation to avoid blocking and thundering-herd notifications
Addressed race conditions in swap/claim approval (optimistic locking or distributed lock)
Discussed notification fan-out at scale (batching, rate limiting, dedupe)
Articulated at least one explicit trade-off with justification (e.g., consistency vs latency, sync vs async)

Structured the interview within time budget, prioritizing high-level design before deep dives
Walked through concrete end-to-end flows (assign, publish, swap) naming specific components/stores touched
Gave a clear, concise opening/closing summary tying design back to core requirements

Problem