Service guide

How to reduce AWS DynamoDB costs

DynamoDB’s pricing model is a choice most teams made once, years ago, under different traffic. Capacity mode, indexes and backups all keep billing exactly as configured — whether or not the workload still looks anything like it did.

The free scan compares consumed against provisioned capacity per table, flags cold GSIs and prices the backup accumulation.

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The DynamoDB checklist

→Provisioned capacity nobody uses. Tables provisioned for launch-day estimates consuming 5% of it since. Consumed-vs-provisioned capacity in CloudWatch tells the story in one graph; autoscaling or a capacity cut follows directly.
→The wrong capacity mode. Rule of thumb: steady, predictable load is cheaper provisioned; spiky or low traffic is cheaper on-demand. Traffic evolved, the mode didn’t — check both directions, the switch is a setting, not a migration.
→Unused global secondary indexes. Every GSI duplicates write costs and storage for its projection. Indexes created for features that changed shape keep billing on every write to the table — query metrics show which indexes nothing reads.
→Backups from another era. On-demand backups do not expire; point-in-time recovery bills continuously per GB. Both accumulate silently on tables whose recovery requirements nobody has restated since setup.
→Hot tables that need caching. Read-heavy tables hammering the same items pay per read for repetition. Sometimes the answer is DAX or an application cache; sometimes it is just noticing one endpoint does 80% of the reads.

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Frequently asked questions

Should we use on-demand or provisioned capacity?

Measure a month of consumed capacity: if usage is steady and utilisation of provisioned capacity would exceed roughly 40–50%, provisioned (ideally with autoscaling) is cheaper; below that, or with spiky unpredictable traffic, on-demand wins. Many accounts have tables on both modes set years ago — the audit checks each table against its actual pattern.

How much do unused GSIs really cost?

A GSI can approach the write cost of the table itself, since every table write propagates to it. On a write-heavy table, one dead index can silently add 30–50% to that table’s bill — for query capability nothing uses. They are the classic invisible DynamoDB expense.

£499 fixed. Free scan first. 20%+ found or it’s free.

The scan is read-only — a role you create and delete, no keys shared — and shows your estimated monthly saving before anyone talks about money.

Run your free scan See pricing