| name | NestJS Search & CQRS |
|---|---|
| description | Elasticsearch integration and Sync patterns. |
| metadata | {"labels": ["nestjs", "search", "elasticsearch", "cqrs"], "triggers": {"files": ["**/*.service.ts", "**/search/**"], "keywords": ["Elasticsearch", "CQRS", "Synchronization"]}} |
Search Engine & Full-Text
Priority: P1 (OPERATIONAL)
Full-text search implementation with Elasticsearch and database patterns.
- 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.
Organization
- Module: Encapsulate the client in a
SearchModule. - Abstraction: Create generic
SearchService<T>helpers. indexDocument(id, body)search(query, filters)- Mapping: Use
class-transformerto map Entities to "Search Documents". Search docs should be flatter than Relational entities constraints.
Testing
- E2E: Do not mock the search engine in critical E2E flows.
- Docker: Spin up
elasticsearch:8container in the test harness to verify indexing works.