Kit Systemdesign Medien und Social

Reference latency and unit tables, assumptions register, QPS, storage, bandwidth, cache, server and cost formulas, worked example, sensitivity, traceability

Per-data-class cache decision: placement, read/write pattern, hit ratio and memory sizing, TTL, invalidation, stampede control, cold start

Social feed: hybrid fan-out on write and read, celebrity threshold, ranking pipeline, feed cache, snapshot pagination, media

Objects and associations model, leader and follower cache tiers, read-after-write, hot vertices, inverse edges, sharding, failure modes

Resumable direct upload, media pipeline, display sizes, storage tiers, 64-bit time-sortable ids, sharded PostgreSQL, celebrity fan-out, CDN

Video upload and ABR streaming: chunked transcoding, renditions ladder, CMAF HLS/DASH, CDN, DRM note, view counts, storage tiers

RTMP, SRT and WHIP ingest, transcoding ladder, LL-HLS and LL-DASH, origin and edge fan-out, latency budget, chat and event sync, VOD archive

Real-time 1:1 and group chat: WebSocket gateways, per-conversation ordering, fan-out, receipts, offline sync, push, E2EE

Push, email, SMS and in-app: templates, preferences and opt-out, priority queues, caps, provider failover, retries, dedup

Transactional email platform: message classes, per-destination queues, RFC 5321 retries, SPF/DKIM/DMARC, IP warm-up, bounces, one-click unsubscribe

Typeahead: trie/FST/edge n-gram index, popularity and recency ranking, query-log pipeline, edge cache, latency budget, safety

Recommender funnel: two-tower retrieval and ANN, pre-ranking and ranking, feature freshness, training, exploration, A/B tests, feedback loops and bias

WebRTC video meetings: mesh vs MCU vs SFU, simulcast layers, bandwidth estimation and layer selection, SFU cascading, raw track recording, SFrame E2EE

Design review checklist in 13 areas, evidence-based scoring rubric, weighted score, red flags, findings register, decision record, 45-minute interview rubric