Read replicas with geo-replication in Azure SQL Database.

You are developing a web application that interacts with an Azure SQL Database. The application will use Entity Framework Core (EF Core) for data access, and you need to optimize performance when executing read-heavy queries. You want to reduce the load on the primary database and improve query performance without compromising data consistency.

Which of the following solutions should you implement?

1. Read replicas with geo-replication in Azure SQL Database.
2. SQL Database elastic pools.
3. Azure Cache for Redis.
4. Table storage with Azure Functions.

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Correct Answer: 1

Explanation:

• Read replicas with geo-replication in Azure SQL Database
  Azure SQL Database supports read replicas and geo-replication, which are designed to improve performance and distribute read-heavy queries across multiple replicas, thus reducing the load on the primary database. By directing read queries to read replicas, you can optimize performance while maintaining data consistency and ensuring the application can scale efficiently.

How it works:

• Read replicas: Azure SQL Database allows you to create read-only replicas of your primary database in different regions or within the same region. These replicas are used specifically to handle read queries, which can significantly offload the primary database and improve the overall performance for read-heavy workloads.
• Geo-replication: When using geo-replication, you can replicate your database to multiple regions, enabling low-latency reads and high availability across regions. This is ideal when your application is global and needs to serve local read queries with minimal latency.

Why the other options aren’t ideal:

1. SQL Database elastic pools (Option 2):
   • Elastic pools are primarily used for managing and scaling multiple SQL databases that have variable usage patterns. While elastic pools are useful for optimizing resource utilization across databases in a pool, they do not directly address read-heavy query performance or offload read traffic from the primary database. They are more about managing and scaling multiple databases, not optimizing read query performance specifically.
2. Azure Cache for Redis (Option 3):
   • Azure Cache for Redis is an in-memory caching service that can be used to cache data and improve performance for frequently accessed data. While it can significantly improve the performance of read operations by caching data, it doesn't directly address offloading read queries from the primary database. Redis is typically used alongside databases to reduce the load on the database by caching results, but it doesn’t provide replication or query distribution capabilities like read replicas do.
3. Table storage with Azure Functions (Option 4):
   • Azure Table Storage is a NoSQL key-value store, which is a different service from Azure SQL Database. It is not a relational database and is not intended for read-heavy SQL-based queries. Azure Functions can be used to process data, but it would not improve SQL query performance or offload traffic from an Azure SQL Database. Additionally, it lacks the ability to replicate or distribute queries like read replicas in SQL Database.

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Key Takeaway:

To optimize performance for read-heavy queries while reducing the load on the primary database, you should use read replicas with geo-replication in Azure SQL Database. This approach will enable you to scale your application efficiently, direct read queries to replicas, and improve query performance without compromising data consistency.