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Difficulty: MediumImproving Database and Caching Efficiency

A high-traffic digital healthcare portal uses an Amazon RDS for PostgreSQL Multi-AZ DB instance to store patient health records and doctor availability schedules. During morning booking hours, the portal experiences a massive surge in traffic. Database metrics show CPU utilization on the DB instance reaching 90%90\% due to a high volume of read-only queries searching for doctor availability. Furthermore, the portal needs to store transient user session data for appointment scheduling workflows. These session states require sub-millisecond read and write latency, and must remain highly available and survive cache node failures. Which combination of database and caching optimization strategies should the Solutions Architect recommend to improve portal performance and manage session state? (Select TWO.)

  1. Deploy an Amazon ElastiCache for Redis replication group with Multi-AZ and automatic failover to store the user session data.Answer
  2. Create one or more Amazon RDS read replicas of the PostgreSQL DB instance, and configure the application to direct doctor availability searches to the replica endpoints.Answer
  3. C
    Deploy an Amazon ElastiCache for Memcached cluster to store the user session states, configuring multi-node sharding to ensure data persistence.
  4. D
    Configure the application to route the read-only doctor availability search queries to the secondary standby instance of the RDS PostgreSQL Multi-AZ deployment.
  5. E
    Deploy an Amazon ElastiCache for Memcached cluster with automatic backup and restore enabled to secure the session states.

Answer

Deploy an Amazon ElastiCache for Redis replication group with Multi-AZ and automatic failover to store the user session data, and create one or more Amazon RDS read replicas of the PostgreSQL DB instance to handle doctor availability searches.
The database read bottleneck is resolved by deploying Amazon RDS read replicas, which offload the read-heavy doctor availability searches from the primary writer instance. The transient session state requirement is addressed by deploying an Amazon ElastiCache for Redis replication group with Multi-AZ and automatic failover, which supports sub-millisecond response times, replication across availability zones, and automatic recovery if a node fails.

Step-by-Step Solution

1
Analyze the database bottleneck and read replication capabilities of the database tier.
Identify that the 90%90\% CPU bottleneck is caused by read-only searches. Creating RDS read replicas will scale reads horizontally, whereas the Multi-AZ standby instance is passive and cannot serve queries.
This offloads read traffic from the primary writer instance, lowering CPU utilization.
2
Evaluate the caching engine properties for storing transient session states that require durability.
Compare Redis and Memcached. Redis supports Multi-AZ replication groups and failover to prevent data loss on node failure, while Memcached is non-persistent and non-replicated.
Choosing ElastiCache for Redis ensures that session data is highly available and survives node failures.

Key Concept

Scaling read-heavy relational workloads with RDS Read Replicas and storing stateful, low-latency transient data using replication-enabled Amazon ElastiCache for Redis clusters.
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Topics

Improving Database and Caching Efficiency