One of the biggest impacts on resource consumption for Azure SQL DB are repeated data pulls by the application layer. No matter how fast those queries execute calling the same procedure or issuing the same SQL statements hundreds, thousands, or million times a day can wreak havoc on database performance. Death by a thousand cuts can easily bring a system to its knees. Sometimes it’s hard for DBAs to troubleshoot these actively as the execution of the statements happens so quickly they don’t even show in tools like sp_whoisactive. It’s not until you begin to dive into things like Query Performance Insights or Query Store that you start to see the real issue.
Azure Portal
SSMS Query Store Top Consuming Queries with Executions Count Metric
The question is how do you combat this issue? The code has been fine-tuned and runs at optimal performance, it’s just the volume of application calls that is causing issues. One answer is Azure Cache for Redis.
What is Azure Cache for Redis?
Simply, it is a dedicated memory cache data store that can be accessed by applications within or outside of Azure based on open source Redis. It enables you to load data into the in-memory data store, read directly from that and reduce the number of calls to your database. Placing the data into this cache layer prevents the application from having to do repeatable data calls over and over again. This can dramatically improve database performance, reduces latency, and frees up resources for other data requests by shifting the performance load to the cache and away from the database layer. This will require changes to your application code; however, it can potentially really increase database performance. You can see an example of a fairly complex app here in Microsoft docs.
This can be not only a performance gain but a monetary one as well. The result could in fact allow you to scale down you Azure SQL Databases because your resource consumption will be reduced.
Getting Started
Create a Resource, Under Databases choose Azure Cache for Redis
Pay attention to the cache type options. Be sure to click the link to the pricing tiers so you can pick the correct one for your environment. In this case I am choosing the cheapest one, Basic C0, which only gets me 250 MB cache but estimated at $16 per month, larger ones can get a little pricey.
For Networking you will have to choose Public or Private Endpoint the choose Next
Now choose which Redis version you want. Note there is a version 6 in Preview. Next will take you to the Tag options, which I skip, because I have no need to Tag my resources. Lastly, we Review and Create the resource. Now that we have a Redis Cache resource created there are a lot more steps to take to be able to use it, store data in it and access it through your applications. I’ll leave those steps to you, in this post I just wanted to show you where to find it in the portal and how to create it.
Summary
If you work within an environment that has repeated data calls thousands of times an hour, this may be a really great resource for you to look into. I highly suggest you add Azure Cache for Redis to your performance tuning tool kit. You can find all the information you need to continue with the process here. Be sure to also read up on all the security things to consider. There is a lot of useful documentation within Microsoft docs that can be found here as well.
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