sd-prep

sources: adhd board hello interview

sources: adhd board hello interview step-by-step print

sources: adhd board hello interview review (v3, 4.75/5)

sources: adhd board hello interview review (v4, 4.7/5)

sources: adhd board hello interview

covers: seat holds with hold_id fencing, the deliberate two-transaction gap, on-sale waiting room, seat-map staleness, outbox and compensation

covers: the connection fleet vs the service fleet, the session registry, the per-conversation seq, idempotent sends, multi-device sync, group fan-out, delivery cursors and presence

covers: 1,000 types means exact counts not a sketch, one row per bucket, local-global aggregation for the hot event type, aligned bucket decomposition, late events, GDPR by crypto-shredding

covers: three tiers by latency, the reversibility asymmetry (orders fail open, egress fails closed), the 10 ms budget, settlement clock and beneficiary cool-off, entity resolution for rings, false positives and the analyst loop

also: notes version (whiteboard voice, facts only)

covers: build once and promote, canary waves and draining a stateful fleet, 4 PB of patch egress, download early and activate late, version skew and expand-migrate-contract, flags as the client's rollback

covers: fifteen-minute staleness as the budget that buys everything, cells not radii and the neighbour boundary bug, density from Manhattan to Montana, target a count not a distance, the cached deck so swipes cost nothing, and trilateration

covers: refusing the delivery-versus-invalidation trade by naming bytes with their own hash, a 400 byte manifest in front of an immutable store, the 50M item cold tail and the regional shield, the hot drop, takedown as refusal not purge, and avatar composition

also: notes version (whiteboard voice, same facts)

covers: server as the only truth for anything scored or spent and inputs as the only thing a client sends for those, matchmaking as placement, the 60 Hz simulate / 20 Hz replicate loop with prediction and reconciliation, the O(N²) bandwidth math and interest management, regions and an edge that terminates but does not simulate, crash to checkpoint to RESUME in ten seconds, cheating versus latency

covers: one topic and five views of it, the execution model, the core objects, keys and ordering and partitioning, delivery semantics, the patterns interviewers listen for, cluster and operations, the configuration cheat sheet

covers: one key and six value shapes, the single-threaded execution model, the commands worth knowing per structure, expiry and eviction, the atomicity toolbox (MULTI, Lua, WATCH), the patterns interviewers listen for, replication and persistence and cluster, the complexity cheat sheet

covers: FOR UPDATE / FOR SHARE / SKIP LOCKED / NOWAIT, the conflict matrix, deadlock ordering, advisory locks, DDL locks, isolation levels, MySQL gap locks