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LangSight supports three storage backends. Switch with one line in .langsight.yaml.

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SQLite (default)

Zero setup. Data stored in ~/.langsight/data.db. 
storage:
  mode: sqlite
  sqlite_path: ~/.langsight/data.db
Best for: local development, single-user CLI use, getting started. Limitations: no langsight costs command (no span tables), no concurrent API access.

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PostgreSQL

For team deployments and the REST API. 
storage:
  mode: postgres
  postgres_url: postgresql://user:password@localhost:5432/langsight
Best for: multi-user API deployments, persistent health history shared across team. Limitations: no langsight costs (tool call spans need ClickHouse).

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ClickHouse

For production scale — required for tool reliability metrics and cost attribution. 
storage:
  mode: clickhouse
  clickhouse_url: http://localhost:8123
  clickhouse_database: langsight
  clickhouse_username: default
  clickhouse_password: ""
Best for: production deployments, langsight costs, reliability analytics, OTLP ingestion at scale. Start ClickHouse with: 
docker compose up -d clickhouse

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Migration path

Development     → SQLite   (zero setup)
Team staging    → Postgres  (shared state)
Production SaaS → ClickHouse (scale + analytics)
Switching is a one-line config change. The StorageBackend protocol ensures all three behave identically from the CLI and API’s perspective.