DynamoDB Throughput Provisioning

DynamoDB throughput provisioning might look bit difficult to understand and hence adding examples.

Throughput Provisioning - Basic Concepts

Provisioned Throughput (Write)

• One write capacity unit (WCU) provides up to one write per second

• Enough for 2.5 million writes per month               

• Price as low as  $0.47 per WCU

Provisioned Throughput (Read)               

• One read capacity unit (RCU) provides

  • two reads per second for eventual consistency reads

  • one read per second for strongly consistent reads

• Enough for 5.2 million reads per month

• Price as low as  $0.09 per RCU

Common Provisioning Errors

1. ProvisionedThroughputExceededException (with HTTP status code 400)

   1. Exceeeded provisioned throughput for a table or one or more GSIs.

Limits

1. An AWS account places some initial maximum limits on the throughput you can provision.

2. You cannot exceed your per-account limits when you add provisioned capacity, and DynamoDB will not permit you to increase provisioned capacity extremely rapidly.

3. You can decrease the ReadCapacityUnits or WriteCapacityUnits settings for a table (UpdateTable operation) up to four times any time per day.

4. If there was no decrease in the past four hours, an additional dial down is allowed, effectively bringing maximum number of decreases in a day to nine times (4 decreases in the first 4 hours, and 1 decrease for each of the subsequent 4 hour windows in a day).

Throughput Provisioning - Important Points

1. All reads are rounded upto 4 KB. 8 KB will require two units.

2. All writes are 1 KB.

3. For any table or global secondary index, the minimum settings for provisioned throughput are 1 read capacity unit and 1 write capacity unit.

4. The provisioned throughput limit includes the sum of the capacity of the table together with the capacity of all of its global secondary indexes.

5. You can increase ReadCapacityUnits or WriteCapacityUnits as often as necessary, using the AWS Management Console or the UpdateTable operation. If you increased your default limits, you can use the DescribeLimits operation to see the current limit values.