Autopilot for Cosmos db – The Cost of Convenience

In the October 2019 update of Azure, Microsoft added ‘Autopilot’ that automatically controls the throughput of a Cosmos d/b. This is handy for unpredictable workloads.. like irregular imports, when you’ll hit the 400 RU maximum and have a Data Factory Pipeline cut out part way.

This can’t be retroactively set on existing Cosmos db containers.. only new ones.

We compared the cost to a d/b with a manual setting of 400 RUs and ran them for a couple of days with no usage.

This it how it looked in Cost Analysis:

Throughput
Daily Cost
Yearly Cost
400 RUs $0.75 $273
600 RUs $1.15 $419
Autopilot 4000 RU max $1.13 $412

As you can see, the standing charge is more expensive for Autopilot… $138/yr more expensive than 400 RUs. But equivalent to running at 600 RUs.

If you have a 400 RU container with predictable high-throughput bursts you can run a script to temporarily increase the RUs, then set them back when you’re done.. that’ll save you money, especially if you have a lot of similarly configured containers.

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