Mailgun is a tool with powerful APIs that allow you to send receive track and store email effortlessly. Except with Zapier you don't have to write any code!
AWS Lambda is a compute service that runs your code in response to events and automatically manages the compute resources for you making it easy to build applications that respond quickly to new information.
PostgreSQL is a powerful open-source database engine with a uniquely advanced query optimizer and dozens of built in features making it an easy choice for production databases.