Right after writing an item, a query on a global secondary index didn't find it in 269 of 300 tries. Secondary indexes are eventually consistent, and "eventually" was longer than one request. What that means for "save, then show the list" screens, what strong consistency costs, and how long adding a new index took.
Our measurements, November 2026.
The full report has the method, what strongly consistent reads cost (twice the read units, no faster), why consistent reads aren't available on global secondary indexes at all, the transaction latency, and what happened when we added a new secondary index to a million-item table.
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DynamoDB vs Postgres, Measured in AWS: 53 Workloads From the Same Client
We ran 53 workloads against RDS Postgres 17 and DynamoDB from one Fargate task in the same Availability Zone, at 100,000, 1 million and 5 million orders. Key lookups took 0.35 ms in Postgres and 2.7 ms in DynamoDB; a two-item transaction 1.75 ms against 20 ms; a question nobody designed for, 0.08–2.7 s against a full table scan. The full results, with the method and every caveat.
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Ad-Hoc Questions on DynamoDB vs Postgres: 16 Analytics Queries at 100,000, 1 Million and 5 Million Orders
Every question across customers is a full table scan in DynamoDB: 217,000 read units at 5 million orders, whether it returns 10 rows or all of them. Postgres answered the same 16 questions in 0.08 to 2.7 seconds without a single index added for them, and an index built in 2.7 seconds took one from 148 ms to 44 ms. Measured in AWS.
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As of November 9, 2026. Provided as is, for general information, and accurate to the best of our knowledge on the date shown. Not legal, compliance, tax, financial or other professional advice. Prices, limits and vendor services change; check current vendor documentation before relying on anything here. Terms of use.