AWS Certified Solutions Architect - Associate

Explanation

Correct Answers: B and D

B. Create a read replica for the DB instance. Configure the application to send read traffic to the read replica.

• This directly addresses the heavy read load issue by offloading read queries from the primary database to one or more read replicas.
• Read replicas in Amazon RDS provide a scalable solution for read-heavy workloads by allowing you to scale out beyond the capacity constraints of a single DB instance.
• This improves performance by distributing read traffic across multiple database instances.

D. Create an Amazon ElastiCache cluster. Configure the application to cache query results in the ElastiCache cluster.

• Caching frequently accessed data in ElastiCache (Redis or Memcached) reduces the number of database queries, which directly alleviates the heavy read load on the RDS instance.
• This improves application performance by serving cached data from memory, which is much faster than querying the database.
• It's particularly effective for read-heavy applications with repetitive queries.

Why other options are incorrect:

A. Turn on auto scaling for the DB instance.

• RDS does not have auto scaling for compute capacity in the same way EC2 does. While you can modify instance types, this is not an automatic scaling solution.
• Vertical scaling (changing instance types) requires downtime and doesn't address read scalability effectively.

C. Convert the DB instance to a Multi-AZ DB instance deployment. Configure the application to send read traffic to the standby DB instance.

• Multi-AZ deployments are primarily for high availability and disaster recovery, not for read scaling.
• The standby replica in Multi-AZ is synchronous and cannot be used for read traffic (except for Aurora with reader endpoints).
• For PostgreSQL RDS, Multi-AZ standby instances cannot serve read traffic.

E. Configure the Auto Scaling group subnets to ensure that the EC2 instances are provisioned in the same Availability Zone as the DB instance.

• While this might reduce network latency slightly, it doesn't address the core issue of database read load.
• This approach also reduces fault tolerance by concentrating resources in a single Availability Zone.
• The performance bottleneck is database read capacity, not network latency between EC2 and RDS.

Key AWS Concepts:

1. RDS Read Replicas: Provide horizontal scaling for read-heavy workloads
2. ElastiCache: In-memory caching service that reduces database load
3. Multi-AZ vs Read Replicas: Multi-AZ is for high availability, read replicas are for read scalability
4. Database Performance Optimization: Combine caching (ElastiCache) with read scaling (Read Replicas) for optimal performance