AWS Lambda: 3 Lessons Learned on Invocations and Tradeoffs Moving from a monolith to an event-driven architecture feels like a superpower until you hit your first production bottleneck. As a Data Engineer currently prepping for the AWS Solutions Architect Associate (SAA) exam, I’ve had to re-evaluate how I trigger my functions. It’s not just about "making it work"; it’s about choosing the right tradeoff between cost, speed, and reliability. Here are my top lessons learned from the trenches. 1. The Cost of Waiting: Synchronous vs. Asynchronous The Lesson: Never make a user (or a calling service) wait for a data-intensive process. In my early projects, I used synchronous calls for almost everything because they were easier to debug. But I learned that synchronous invocations: Increase Costs: You pay for the idle time of the calling service. Create Fragility: If the Lambda fails, the upstream service fails too. The Tradeoff: We moved to Asynchronous Invocations ( --invocation-type Event ).…