How can I avoid Azure SQL serverless cold-start timeouts without increasing costs?
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MellowCactus42
I'm testing a mobile app that isn't deployed yet, and I'm currently the only user. When I open it for the first time after the database has been inactive for roughly a day, the app sometimes reports a connection timeout. Since the database uses a serverless tier, I assume it has been paused and needs time to start again. Is there a way to periodically wake it up or otherwise reduce the initial delay without significantly increasing my Azure bill?
Answers
If you need relational SQL without startup delays, moving to a small provisioned tier is probably the simplest solution. For workloads that don’t require SQL, lower-cost options such as a free NoSQL tier or inexpensive key-value storage may also work, but they would require changing the application’s data model.
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The cold start is the tradeoff for serverless pricing. If you keep the database warm continuously, you’ll use up any free compute allowance quickly and may pay more. For a small always-on database, a low-tier provisioned or DTU-based plan may be a better option. The cheapest tier is less powerful and has limited storage, but it avoids cold starts and can cost only a few dollars per month.
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You can run a query every few hours or disable the automatic pause feature, but keeping the database active means you’ll be billed for compute instead of benefiting from serverless pausing.
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A scheduled health check could periodically connect to the database and run a lightweight query. However, that only prevents or delays the pause; it doesn’t remove the cost. You could also add connection retry logic so the app waits and tries again when the database is waking up.
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MellowCactus42: That makes sense. I’ll compare the small provisioned tiers with the current serverless setup and see whether the predictable monthly cost is worth avoiding the timeout.