SAP-C02 Q557 · Database

Question

A SaaS web app runs on EC2 Linux behind an ALB. It storesuser sessionsin an RDS Multi-AZ database. During high traffic, the app suffers latency due to session read/write. What is the best way to reduce session latency?

Accepted Answer

**D. Use ElastiCache for Redis to store sessions.**

**Step-by-step reasoning:**

1. **Problem identification**: The bottleneck is session read/write latency against RDS during high traffic. Sessions are small key-value pairs (session ID → session data) that are read on every request and written frequently.

2. **Why in-memory is the answer**: Session data is a classic use case for in-memory data stores. Redis operates entirely in memory, delivering **sub-millisecond latency** compared to RDS disk-based reads/writes that can be several milliseconds or more under load.

3. **Why Redis specifically**: Redis supports data structures (hashes, strings), automatic TTL-based expiration (perfect for session timeouts), replication for HA, and persistence options. It's purpose-built for session mana

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