Recently, one of my friend/client came up with the scenario below. Scenario: There is a lambda function, which calls to a external API and fetch some data. This external API only accepts incoming requests only from pre-configured whitelisted IPs. As per today, AWS doesnt’ support elastic IPs for Lambda. However, there is a simple work around. Solution: Simple solution is, to create the lambda function within a VPC and make the 3rd party API to be accessible via a NAT gateway.

IAM Policy version is a useful feature in IAM when try to identify the correct access rights for a particular policy and switch between the changes applied to the policies. Please Note: Policy versions are not available for inline policies. When you update a particular customer manage policy, AWS will not over-write the existing policy. But new version is created and set as the default version. Image: Policy versions listing for a single IAM Policy

Lambda by nature is highly scalable. However there ares some limitations you need to consider when there are lot of Lambda functions run simultaneously. Please note: This will not applicable for all the scenarios, but for a system with a high throughput. Account Level Concurrent Execution Limit As at now, Lambda has a soft limit of 1000 concurrent executions per region. Which means, at any given moment, sum of lambda executions running belongs to all of your lambda functions in a single region must be less than 1000.