Scaling with a Sliding Time Window

Use when only recent data needs fast search -- social media posts, news articles, support tickets, logs, job listings. Old data either becomes irrelevant or can tolerate slower access.

Three strategies: shard rotation (recommended), collection rotation (when per-period config differs), and filter-and-delete (simplest, for continuous cleanup).

Shard Rotation (Recommended)

Use when: data has natural time boundaries (daily, weekly, monthly). Preferred because queries span all time periods in one request without application-level fan-out. User-defined sharding

1. Create a collection with user-defined sharding enabled
2. Create one shard key per time period (e.g., 2025-01, 2025-02, ..., 2025-06)
3. Ingest data into the current period's shard key
4. When a new period starts, create a new shard key and redirect writes
5. Delete the oldest shard key outside the retention window