Persistence (Developer Guide)

What It Does

The historical cache stores normalized bars and watermarks to reduce REST calls and make backtests deterministic.

Why It Exists

FYERS history calls are rate limited and can be slow. A cache makes repeated runs predictable and cheaper.

Config Dependencies

• config/cache.yaml
• config/nse_calendar.yaml

With Backtrader

The Store uses the cache automatically when you call get_history(...).

Without Backtrader

You can instantiate SQLiteHistoricalCache directly if needed.

Limitations

• Cache is rebuildable and not a source of truth.
• SQLite allows one writer; multi-process writes require careful tuning.

Scenario Example

Scenario: You need to wipe history data without affecting live state. - Delete only the cache DB path from cache.yaml. - Do not delete the state DB.