IAM Policy Versioning

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

Understanding Lambda Concurrency

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.