Search Engine & Full-Text

Strategy

• Pattern: CQRS (Command Query Responsibility Segregation).
  • Write: To Primary Database (Postgres/MySQL). Source of Truth.
  • Read (Complex): To Search Engine (Elasticsearch, OpenSearch, MeiliSearch). Optimized for filtering, fuzzy search, and aggregation.

Synchronization (The Hard Part)

• Dual Write (Anti-Pattern): await db.save(); await es.index();.
  • Why: Partial failures leave data inconsistent. Slows down HTTP response.
• Event-Driven (Recommended):
  1. Service writes to DB.
  2. Service emits EntityUpdated.
  3. Event Handler (Async) pushes to Queue (BullMQ).
  4. Worker indexes document to Search Engine with retries.
• CDC (Golden Standard): Change Data Capture (Debezium). Connects directly to DB transaction log. No app conceptual overhead, but higher ops complexity.