Why is my AWS DynamoDB cost so high?

See what changed in your AWS bill

If you're wondering “why is my DynamoDB bill so high”, it's usually due to increased request volume or inefficient query patterns.

If your AWS bill suddenly went up, DynamoDB is often one of the hidden reasons. Costs can rise alongside other services like RDS, NAT Gateway, CloudWatch, or Lambda spikes.

DynamoDB usage often grows quietly in the background as your application scales. Unlike fixed-cost services, DynamoDB scales automatically, which means costs can increase without any obvious change to your infrastructure.

Many developers don’t notice DynamoDB cost increases until traffic grows, new features are deployed, or inefficient queries begin to generate significantly more read and write operations.

Simple explanation: DynamoDB costs increase when read and write usage grows, storage expands, or on-demand activity becomes more expensive than expected.

Example DynamoDB cost spike

Last month: £18

This month: £95

  • Application traffic increased
  • More read and write requests
  • Storage size grew over time

Result: More table activity → higher DynamoDB cost


Recommendations:

  • Review table traffic patterns
  • Check whether on-demand is still the best fit
  • Remove unused tables and indexes
  • Monitor read and write growth

What actually drives DynamoDB costs

DynamoDB pricing is mainly based on read requests, write requests, and storage. If your application becomes more active or your queries become less efficient, your costs will rise accordingly.

On-demand mode can also become expensive at scale, especially if traffic spikes suddenly.

How to check DynamoDB costs in AWS

You can find DynamoDB costs in AWS Cost Explorer by filtering by service. Look for increases in read requests, write requests, and storage usage.

You can also check individual tables in the DynamoDB console to see which ones are generating the most traffic and contributing to your bill.

How to reduce DynamoDB costs

Why this catches people off guard

DynamoDB can scale quickly with application growth, so costs often rise quietly until request volume becomes much higher than expected.

See exactly what changed in your AWS bill

Frequently asked questions

Why is AWS DynamoDB so expensive?

DynamoDB becomes expensive when read and write traffic increases.

Can DynamoDB costs increase suddenly?

Yes, usually after traffic spikes or deployments.

Does on-demand DynamoDB cost more?

It can. On-demand pricing is flexible and useful for unpredictable traffic, but it may become more expensive than provisioned capacity if your workload is consistently high.

How do I see which DynamoDB table costs the most?

You can use AWS Cost Explorer for service-level cost trends and the DynamoDB console to review which tables have the most read, write, and storage activity.

Is DynamoDB cheaper than RDS?

It depends on the workload. DynamoDB can be cheaper for some use cases, but for high request volumes or poorly optimised access patterns, it can become expensive.

How do I reduce DynamoDB costs without breaking my app?

Start by reviewing traffic patterns, removing unused tables or indexes, improving query efficiency, and checking whether provisioned capacity would be cheaper than on-demand.

Is DynamoDB free in AWS?

AWS offers a limited free tier for small workloads, but once your application grows beyond that level, DynamoDB costs can increase quickly.