Using AWS managed services for high availability

Can you describe what high availability means in the context of AWS managed services?

High availability in the context of AWS managed services refers to a system design that ensures a pre-defined level of operational performance, usually uptime, for a higher-than-normal period. AWS managed services achieve this through redundant or failover components, such as multi-AZ deployments, auto-scaling, and using services like Amazon RDS, which handles database failover automatically.

How does Amazon RDS provide high availability, and what are the steps to enable it?

Amazon RDS provides high availability through its Multi-AZ deployments where it automatically provisions and maintains a synchronous stand-by replica in a different Availability Zone (AZ). To enable it, when creating a database instance, simply select the Multi-AZ deployment option, and AWS handles the rest, including failover, without manual intervention.

What role does Amazon Route 53 play in maintaining high availability for your AWS applications?

Amazon Route 53 plays a critical role in maintaining high availability by providing a highly available and scalable Domain Name System (DNS) service. It routes end-user traffic to the proper endpoints, can perform health checks on resources, and supports DNS failover, which helps redirect traffic to healthy endpoints in case of any failures, ensuring minimal interruption.

Explain the difference between scalability and high availability in AWS managed services.

Scalability is about the capability of a system to grow and handle an increasing amount of work by adding resources. High availability, on the other hand, is about ensuring that the system remains operational, with minimal downtime, even during failures. AWS managed services provide both by allowing systems to scale up or out (elasticity) and to continue operating through redundant components or across multiple AZs for high availability.

How do you implement high availability for a stateless application using AWS services?

To implement high availability for a stateless application, you would typically use a combination of AWS Elastic Load Balancing to distribute traffic, Amazon EC2 instances located in multiple Availability Zones, and Auto Scaling to adjust the number of instances dynamically. This setup ensures that if one AZ or instance fails, the application remains available.

Describe how the AWS Shared Responsibility Model impacts the management of high availability.

The AWS Shared Responsibility Model stipulates that AWS is responsible for the availability of the infrastructure that runs all of the services offered in the AWS Cloud. On the other hand, the customer is responsible for implementing high availability features at the application level. This means that while AWS provides the tools and services for high availability (such as redundant data centers), it’s up to the customer to correctly configure and use these services.

How does the deployment of AWS Lambda functions relate to high availability?

AWS Lambda inherently provides high availability because it runs your code in response to events across multiple AZs within a region. There’s no need to provision or manage infrastructure, and Lambda automatically scales and manages compute resources, making the functions highly available without needing user intervention.

What AWS service would you recommend for high availability of in-memory caching?

For in-memory caching, AWS recommends using Amazon ElastiCache. This service improves the performance of web applications by allowing you to retrieve information from fast, managed in-memory caches, rather than relying on slower disk-based databases. ElastiCache can be run in a clustered mode across multiple AZs for high availability.

How does AWS’s global infrastructure contribute to achieving high availability?

AWS’s global infrastructure, with its multiple geographic regions and Availability Zones, contributes to high availability by allowing applications to be deployed across physically separate locations. By leveraging this infrastructure, applications can be architected to withstand failures of individual servers, data centers, or entire regions, minimizing the impact on end-users.

What steps should you take to ensure high availability when using Amazon EC2 instances?

To ensure high availability using Amazon EC2, you should deploy instances across multiple Availability Zones, architect a fault-tolerant VPC, utilize Elastic Load Balancers to distribute traffic, implement Auto Scaling to handle changes in load, and use Amazon Machine Images (AMIs) for rapid recovery or scaling.

Why is data replicability important for high availability in AWS, and which services can you use to achieve it?

Data replicability is important because it ensures that there is no single point of failure for data storage and access. Services like Amazon S3, with its cross-region replication feature, and Amazon RDS, with its Multi-AZ and Read Replica functionalities, support data replicability. This allows for the preservation of data and accessibility even in the face of component failures.

What disaster recovery strategies does AWS recommend for high availability?

AWS recommends various disaster recovery strategies to ensure high availability, such as Pilot Light (a minimal version of the environment always running), Warm Standby (a scaled-down but fully functional version of the environment), Multi-Site (active-active configuration), and Backup and Restore. The choice of strategy will depend on the business’s recovery time and recovery point objectives (RTO/RPO).