Which configuration is effective for improving the availability of an RDS database and automatically failing over to a standby instance in a different Availability Zone when the primary instance fails?
A question asking to select the RDS configuration that improves availability and provides automatic failover.
Multi-AZ deployment
This is correct. RDS Multi-AZ deployment is a high-availability configuration that maintains a synchronously replicated standby instance in a separate AZ and automatically fails over during a failure. Its purpose is to improve availability and minimize downtime during planned maintenance or instance failures.
Read replica
A read replica is a replica for distributing read traffic, and its primary purpose is scalability.
Its purpose differs from Multi-AZ, which is aimed at improving availability through automatic failover, so this is incorrect.
Place a load balancer in front of the database to distribute connections.
A load balancer (ELB) distributes traffic to computing resources such as EC2. Failover for RDS is performed via Multi-AZ configuration and DNS failover.
Placing an ELB in front of the database to automatically switch to a standby is not an RDS availability improvement approach, so this is incorrect.
Taking a snapshot
A snapshot is a backup that requires time to restore.
It cannot meet the requirement of instantly and automatically switching to a standby upon failure, so this is incorrect.
RDS Multi-AZ = availability (automatic failover to a standby in a different AZ); Read replica = read scalability. Distinguish by purpose: availability vs. performance.