Infrequently accessed data stored in Azure Cosmos DB

Explanation

Why the waste happens and who it affects.

Yet in many environments, cold data such as logs, telemetry, or historical records is retained in Cosmos DB due to a lack of lifecycle management.

The pricing dimensions that drive this cost.

Cosmos DB charges include:

Data storage billed per GB per month, across all regions where data is replicated
Manual provisioned throughput (RU/s), billed per hour for the RU/s provisioned regardless of actual usage; autoscale is billed per hour for the highest RU/s scaled to (never below 10% of the configured maximum), and serverless is billed per RU consumed
Backup storage billed separately (if configured)
Serverless mode available, but subject to limitations on scaling and total RU consumption

Storing cold data incurs persistent storage charges and may inflate RU requirements unnecessarily.

4 checks to find it in your estate.

Identify Cosmos DB resources (e.g., containers, collections, or tables) with high storage usage but low request volume
Use Azure Monitor, diagnostic logs, or Azure Cosmos DB insights to assess read/write activity over time
Evaluate whether the data is actively queried or needed for operational workloads
Check whether data retention or lifecycle policies are defined for the resource

7 ways to remove the waste.

Export infrequently accessed data to lower-cost storage services:
Use Blob Storage Cool for rarely accessed but readily retrievable data
Use Blob Storage Archive for long-term retention with delayed retrieval
Use Azure Table Storage for simple key/value access when global distribution is unnecessary
Delete cold data from Cosmos DB after successful archival
Implement data lifecycle automation to routinely transition stale data out of Cosmos DB
Set a time to live (TTL) on containers or items so Cosmos DB automatically deletes cold data after a set period once it is archived or no longer needed

Vendor references for pricing and configuration.