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

Create one shard key per time period, write to the current one, and delete the oldest shard key once it leaves the retention window. The Time-Based Sharding tutorial walks through the setup.

• Deleting a shard key reclaims all resources instantly (no fragmentation, no optimizer overhead)
• Pre-create the next period's shard key before rotation to avoid write disruption
• Use shard_key_selector at query time to search only specific periods for efficiency
• Shard keys can be placed on specific nodes for hot/cold tiering