midMongoDB
What are TTL Indexes?
Updated May 1, 2026
Short answer
TTL (Time To Live) indexes automatically remove documents from a collection after a certain amount of time.
Deep explanation
They are used on a Date field. A background thread runs every 60 seconds to delete expired documents.
Real-world example
Automatically deleting user session data or temporary OTPs.
Common mistakes
- Setting TTL on a field that isn't a Date type (the index won't work).
Follow-up questions
- Does TTL guarantee immediate deletion?