Database & Caching
SQL, isolation levels, Redis, migrations, Elasticsearch.
1. SQL Indexing & Optimization
B-tree, composite, covering and partial indexes, leftmost prefix, EXPLAIN ANALYZE, join algorithms, keyset pagination, statistics, partitioning, sargability and slow-query scenarios across PostgreSQL and MySQL.
2. Transactions & Isolation Levels
ACID, isolation anomalies, MVCC, locking, SELECT FOR UPDATE and SKIP LOCKED, deadlocks, optimistic locking, idempotency, distributed transactions and replication lag scenarios.
3. Hibernate Performance Tuning
JDBC batching, ID generation, projections, second-level and query caches, flush behaviour, bulk operations, statement caching and connection pool sizing for Hibernate 6.
4. Redis & Caching Strategies
Redis data structures, caching patterns, eviction, persistence, high availability, distributed locks, rate limiting, hot/big keys, cache failure modes and Spring Data Redis with Lettuce.
5. Cache Invalidation Scenarios
Stale reads, dual-write races, CDC and event-based invalidation, versioned keys, multi-layer caches, consistency trade-offs, warm-up and failover behaviour.
6. Flyway/Liquibase Migrations
Versioned and repeatable migrations, expand-contract zero-downtime changes, checksum failures, rollbacks, large-table changes, baselining, CI practices and multi-instance startup locking.
7. Elasticsearch Basics
Inverted index, analyzers, mappings, BM25 relevance, shards and replicas, near-real-time refresh, bool queries, aggregations, search_after pagination, syncing from a database, cluster health and when not to use it.