DynamoDB ADD operation throttling thresholds under high-concurrency atomic increments

Atomic counter increments using UpdateItem ADD may encounter unexpected throttling

When performing high-throughput atomic counter increments with the ADD operation in DynamoDB, applications can experience throttling that does not align with provisioned throughput expectations. The ADD operation is documented as atomic, but under sustained write loads exceeding ~1000 writes per second to a single item, clients observe ConditionalCheckFailedException and ThrottlingException errors that vary by region and capacity mode.

Key constraints include: provisioned versus on-demand capacity modes exhibit different throttling behaviors; client-side retry logic with exponential backoff is recommended but may not prevent throttling under sustained load; and AWS documentation does not explicitly define maximum concurrent writers for atomic operations on a single item.

Monitoring CloudWatch metrics for ConditionalCheckFailedRequests during concurrent writes could help identify the actual throughput limits, but these thresholds appear to shift based on table configuration and regional capacity.

What is the documented maximum sustained write throughput for UpdateItem ADD operations on a single item, and how do throttling thresholds differ between provisioned and on-demand capacity modes in different AWS regions?