What problem does it solve? Designing reliable data persistence is hard: poorly indexed queries cause slow sequential scans, and misconfigured caches lead to stale data, stampedes, and out-of-memory crashes. This Skill guides the design of database schemas, indexing strategies, and cache invalidation flows that protect data integrity while optimizing retrieval. ## Core Features & Use Cases - Schema & Index Design: Outline PostgreSQL/SQLite schemas, composite B-tree indexes, and transaction boundaries with ACID guarantees. - Caching Topology: Implement cache-aside, write-through, and write-behind patterns with LRU eviction, TTLs, and stampede mitigation via mutex locks or probabilistic early expiration. - Mobile & Sync Persistence: Apply CoreData/SwiftData background concurrency rules, batch mutations, and offline sync with CRDTs or ETag conflict handling. - Use Case: When building a high-read user profile service, use this Skill to define a composite index on queried columns and a Redis cache-aside flow that populates on miss and invalidates keys on writes. ## Quick Start Ask the agent to design a PostgreSQL schema with composite indexes and a Redis cache-aside invalidation strategy for your high-read query service.