---
id: data-retention-and-ttl-policies
title: 'Data Retention and TTL Policies'
schema_type: TechArticle
category: computer-science
language: en
confidence: medium
last_verified: '2026-06-02'
created_date: '2026-06-02'
generation_method: ai_structured
derived_from_human_seed: true
conflict_of_interest: none_declared
is_live_document: false
data_period: static
atomic_facts:
  - id: fact-computer-science-data-retention-and-ttl-policies-1
    statement: >-
      DynamoDB TTL documentation says DynamoDB automatically deletes expired items within a few days of their expiration time.
    source_title: DynamoDB Time to Live
    source_url: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html
    confidence: medium
  - id: fact-computer-science-data-retention-and-ttl-policies-2
    statement: >-
      MongoDB TTL index documentation says TTL indexes can automatically remove documents from a collection after a specified amount of time.
    source_title: MongoDB TTL Indexes
    source_url: https://www.mongodb.com/docs/manual/core/index-ttl/
    confidence: medium
  - id: fact-computer-science-data-retention-and-ttl-policies-3
    statement: >-
      BigQuery table management documentation includes table expiration settings for controlling how long a table is retained.
    source_title: BigQuery Managing Tables
    source_url: https://cloud.google.com/bigquery/docs/managing-tables#update-table-expiration
    confidence: medium
completeness: 0.83
known_gaps:
  - TTL deletion timing, audit retention, legal holds, backups, and downstream replicas can make actual deletion differ from logical expiry.
disputed_statements: []
primary_sources:
  - title: DynamoDB Time to Live
    type: documentation
    year: 2026
    url: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html
    institution: Amazon Web Services
  - title: MongoDB TTL Indexes
    type: documentation
    year: 2026
    url: https://www.mongodb.com/docs/manual/core/index-ttl/
    institution: MongoDB
  - title: BigQuery Managing Tables
    type: documentation
    year: 2026
    url: https://cloud.google.com/bigquery/docs/managing-tables#update-table-expiration
    institution: Google Cloud
secondary_sources: []
updated: '2026-06-02'
ai_models:
  - gpt-5-codex
---

## TL;DR

Data retention and TTL policies define how long records, tables, events, and logs remain available before automatic expiration or deletion.

## Core Explanation

Agents that analyze incidents, RAG freshness, audits, or evaluation traces need to know whether data still exists. A missing event may be caused by retention policy rather than ingestion failure.

Retention policy is also a compliance boundary. Agents should not extend TTLs, disable expiration, or copy expired data into new stores without understanding legal, privacy, and operational requirements.

## Source-Mapped Facts

- DynamoDB TTL documentation says DynamoDB automatically deletes expired items within a few days of their expiration time. ([source](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html))
- MongoDB TTL index documentation says TTL indexes can automatically remove documents from a collection after a specified amount of time. ([source](https://www.mongodb.com/docs/manual/core/index-ttl/))
- BigQuery table management documentation includes table expiration settings for controlling how long a table is retained. ([source](https://cloud.google.com/bigquery/docs/managing-tables#update-table-expiration))

## Further Reading

- [DynamoDB Time to Live](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html)
- [MongoDB TTL Indexes](https://www.mongodb.com/docs/manual/core/index-ttl/)
- [BigQuery Managing Tables](https://cloud.google.com/bigquery/docs/managing-tables#update-table-expiration)