DOP-C02 Question 155
Select 2You are managing a stateful service running on Amazon EC2 instances behind an Auto Scaling group. The service stores user session data on instance volumes. To ensure high availability in case of instance failure, you need to implement a fault-tolerant architecture that replicates stateful data and allows seamless failover. Which of the following approaches should you implement?
- A
Use Amazon Elastic File System (EFS) to store session data and mount it to all instances.
- B
Configure Amazon RDS with Multi-AZ deployment to store and replicate session data.
- C
Store session data on instance store volumes and configure Auto Scaling Lifecycle Hooks to back up the data to S3 on instance termination.
- D
Use DynamoDB as a centralized store for session data with eventual consistency enabled.
- E
Set up a custom replication mechanism between EC2 instances to sync data across their instance volumes.
Show answer and explanation
Correct answers: A, D
Explanation
To ensure high availability and fault tolerance for stateful services, it is important to use solutions that provide built-in replication and high durability. Amazon EFS allows session data to be shared across multiple instances, enabling seamless failover. DynamoDB, as a managed NoSQL database, can also store session data centrally, offering high availability and scalability. These approaches are better suited for the scenario compared to ephemeral storage or custom replication mechanisms.
- A. Correct.
Amazon EFS is a managed, highly available file system that can be mounted across multiple EC2 instances, making it a good choice for sharing stateful data across instances and enabling fault tolerance.
- B. Incorrect.
Amazon RDS is primarily used for relational databases and not for session data storage in this scenario. While Multi-AZ deployment ensures high availability for database workloads, it is not the best fit for replicating ephemeral session data.
- C. Incorrect.
Instance store volumes are ephemeral and not designed for long-term storage or replication. While backing up data to S3 on termination can help preserve data, it does not support seamless failover for a stateful service.
- D. Correct.
DynamoDB is a fully managed NoSQL database that is well-suited for storing session data. With its high availability and consistent performance, it can serve as a centralized store for session data, making it a viable option for replication and failover.
- E. Incorrect.
Custom replication mechanisms between EC2 instance volumes are complex to implement and maintain. They are generally not recommended when managed solutions like EFS or DynamoDB are available.