Lambda function design
Most architectures should prefer many, shorter functions over fewer, larger ones. Making Lambda functions highly specialized for your workload means that they are concise and generally result in shorter executions. The purpose of each function should be to handle the event passed into the function, with no knowledge or expectations of the overall workflow or volume of transactions. This makes the function agnostic to the source of the event with minimal coupling to other services.
Any global-scope constants that change infrequently should be implemented as environment variables to allow updates without deployments. Any secrets or sensitive information should be stored in AWS Systems Manager Parameter Store or AWS Secrets Manager