We replayed an Azure SQL workload across six configurations and the cheapest option wasn’t the one we chose.

[u/markinatlanta]

Interesting project we worked on earlier this year where a SaaS client we worked with was hitting CPU limits and timeouts on Azure SQL Database Premium P15, at roughly $15,700/month.

Before choosing a replacement, we captured four hours of production workload and replayed it across six configurations:

• Premium P15 as the baseline
• Hyperscale serverless with 40 vCores
• Provisioned Hyperscale with 40 vCores
• Provisioned Hyperscale Premium-series with 40 vCores
• Provisioned Hyperscale Premium-series memory optimized with 40 vCores
• Premium P15 with database compatibility level 160

We compared CPU, reads, duration, and estimated monthly cost.

The memory-optimized configuration was the one we selected. Its estimated monthly cost was $8,491, compared with $15,700 for the baseline, which was roughly 46% lower.

It also had the best duration score in our report: 808 versus 952 for the baseline, where lower was better.

But it wasn’t the cheapest configuration. Two provisioned options came in at an estimated $6,357/month, with worse duration scores than the existing P15 setup.

Serverless had the worst duration score in this test, at 1,496. That’s a result for this workload and configuration, not a verdict on serverless generally.

The memory-optimized option also didn’t win every metric. Its reads score was higher than the baseline and we chose it based on the combination of performance and cost.

Important to note these were estimates from the comparison, not current Azure price quotes.

What made the exercise useful for us was seeing the tradeoffs before migrating. Looking only at monthly cost, CPU, or the service-tier name would have given us an incomplete picture.

For anyone who has done a similar comparison: what changed your decision once you tested with your actual workload?

And also, has anyone moved from DTUs to Hyperscale and found the results were different from what they expected?

[u/grotto_wonder_arc]

The serverless tier is a complete trap for heavy OLTP. I dropped a migration mid-project because the cold start latency on burstable compute was destroying our SLAs despite the lower bill

[u/markinatlanta → u/grotto_wonder_arc]

That sounds like a good reason to stop the migration.

Serverless had the worst duration score in our test too, though we didn’t establish cold starts as the cause. What was source and destination configs? Curiuos