How to choose between provisioned throughput and serverless

APPLIES TO: NoSQL MongoDB Cassandra Gremlin Table

Azure Cosmos DB is available in two different capacity modes: provisioned throughput and serverless. You can perform the exact same database operations in both modes, but the way you get billed for these operations is radically different. The following video explains the core differences between these modes and how they fit different types of workloads:

Detailed comparison

Criteria	Provisioned throughput	Serverless
Best suited for	Workloads with sustained traffic requiring predictable performance	Workloads with intermittent or unpredictable traffic and low average-to-peak traffic ratio
How it works	For each of your containers, you configure some amount of provisioned throughput expressed in Request Units (RUs) per second. Every second, this quantity of Request Units is available for your database operations. Provisioned throughput can be updated manually or adjusted automatically with autoscale.	You run your database operations against your containers without having to configure any previously provisioned capacity.
Geo-distribution	Available (unlimited number of Azure regions)	Unavailable (serverless accounts can only run in a single Azure region)
Maximum storage per container	Unlimited	1 TB1
Performance	< 10-ms latency for point-reads and writes covered by SLA	< 10-ms latency for point-reads and < 30 ms for writes covered by SLO
Billing model	Billing is done on a per-hour basis for the RU/s provisioned, regardless of how many RUs were consumed.	Billing is done on a per-hour basis for the number of RUs consumed by your database operations.

¹ Serverless containers up to 1 TB is GA. Maximum RU/sec availability is dependent on data stored in the container. See, Serverless Performance

Estimating your expected consumption

In some situations, it may be unclear whether provisioned throughput or serverless should be chosen for a given workload. To help with this decision, you can estimate your overall expected consumption, or the total number of RUs you may consume over a month.

For more information, see estimating serverless costs.

Example 1: a workload is expected to burst to a maximum of 500 RU/s and consume a total of 20,000,000 RUs over a month.

• In provisioned throughput mode, you would configure a container with provisioned throughput at a quantity of 500 RU/s for a monthly cost of: $0.008 * 5 * 730 = $29.20
• In serverless mode, you would pay for the consumed RUs: $0.25 * 20 = $5.00

Example 2: a workload is expected to burst to a maximum of 500 RU/s and consume a total of 250,000,000 RUs over a month.

• In provisioned throughput mode, you would configure a container with provisioned throughput at a quantity of 500 RU/s for a monthly cost of: $0.008 * 5 * 730 = $29.20
• In serverless mode, you would pay for the consumed RUs: $0.25 * 250 = $62.50

(These examples aren't accounting for the storage cost, which is the same between the two modes.)

Pastaba

The costs shown in the previous example are for demonstration purposes only. See the pricing page for the latest pricing information.

Next steps

• Read more about provisioning throughput on Azure Cosmos DB
• Read more about Azure Cosmos DB serverless
• Get familiar with the concept of Request Units