How does DynamoDB partition data, and what limits apply per partition?

Summary

DynamoDB hashes the partition key to place items on partitions (storage units of up to about 10 GB). Each partition supports up to 3,000 read capacity units and 1,000 write capacity units per second. Tables split partitions automatically as data or traffic grows.

Longer Answer

Because limits are per partition, a table with huge total capacity can still throttle if one partition key receives a disproportionate share of traffic. DynamoDB mitigates this with adaptive capacity (shifting capacity to hot partitions) and split for heat (splitting busy partitions, which only helps if traffic is spread across sort keys rather than a single item). A single item can never exceed those per-partition limits.

Key Points

• Hash of PK chooses the partition.
• ~10 GB, 3,000 RCU and 1,000 WCU per partition.
• Automatic splits; adaptive capacity.
• A single hot key is still capped.