Search, Geospatial & Real-Time

Trie data structure, top-k per prefix, Redis sorted sets, batch + real-time data pipeline, and personalization

Lat/lng to string encoding, prefix property, 9-cell proximity search, Redis GEO commands, and limitations at high latitudes

Adaptive 2D spatial partitioning, dynamic subdivision, range queries with pruning, and QuadTree vs GeoHash trade-offs

High write-rate GPS ingestion, GeoHash cells in Redis sorted sets, stale cleanup, H3 hexagonal grid, and hot cell mitigation

Heartbeat-based detection, Redis TTL auto-expiry, fan-out optimization via scoped pub/sub, flapping prevention, and multi-device presence

Fan-out on write vs read, hybrid approach for celebrities, APNs/FCM push delivery, deduplication with Redis SETNX, and per-user rate limiting

Stateful connection management, sticky sessions, cross-server routing via Redis Pub/Sub, session registry externalization, and heartbeat with exponential backoff reconnection

Lightweight IoT pub/sub protocol, QoS levels (0/1/2), retained messages, Last Will and Testament, persistent sessions, broker clustering, and MQTT vs WebSockets

Double-entry bookkeeping, idempotency keys for safe retries, outbox pattern for distributed transactions, nightly reconciliation, and PCI scope reduction via tokenization

Redis sorted set delayed queues, atomic poll with Lua scripts, lease-based at-least-once delivery, leader-based distributed cron, and per-tenant fair scheduling

UUID v4 randomness vs B-tree fragmentation, Snowflake 64-bit sortable IDs, ULID timestamp+random, database sequences, and clock skew mitigations