High Availability - Serverless Architectures with AWS Lambda

High Availability

High-availability is important for production applications. The availability posture of your Lambda function depends on the number of Availability Zones it can be executed in. If your function uses the default network environment, it is automatically available to execute within all of the Availability Zones in that AWS Region. Nothing else is required to configure high availability for your function in the default network environment. If your function is deployed within your own VPC, the subnets (and their respective Availability Zones) define if your function remains available in the event of an Availability Zone outage. Therefore, it’s important that your VPC design includes subnets in multiple Availability Zones. In the event that an Availability Zone outage occurs, it’s important that your remaining subnets continue to have adequate IP addresses to support the number of concurrent functions required. For information on how to calculate the number of IP addresses your functions require, see this documentation.