TL;DR: Here's the math that pushed me off EC2: a t3. micro instance runs you roughly $8-10/month whether it serves zero requests or ten thousand.

📖 Reading time: ~30 min

What's in this article

The Problem: Your Flask App Works Locally, Now What?

How Lambda Actually Runs Your Flask App (Understand This First)

Prerequisites and Local Setup

Step 1 — Build a Minimal Flask App Worth Deploying

Step 2 — Package Dependencies Correctly (Where Most Tutorials Fail)

Step 3 — Write the SAM Template (template.yaml)

Step 4 — Deploy and Test

Gotchas I Hit That Aren't in the AWS Docs

The Problem: Your Flask App Works Locally, Now What?

Here's the math that pushed me off EC2: a t3.micro instance runs you roughly $8-10/month whether it serves zero requests or ten thousand. Lambda charges $0.20 per million invocations plus compute time billed in 1ms increments.…