Key lookups in Postgres went from 0.16 ms to 9.75 ms, about 60 times slower, while four reporting queries ran on the same 2-vCPU instance. In DynamoDB, lookups stayed at 2.5 ms during a parallel scan of the same table. And what a jump from 10 to 1,000 concurrent clients did to each.
Alone
During a report
Median key lookup, alone and while reporting queries run against the same database (log scale). Our measurements, November 2026.
This is the strongest case for keeping analytics off your primary database, or for DynamoDB's isolation. The full report has p99s, the spike test second by second, and the usual fixes: read replicas, exports and separate analytics stores.
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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.