And why your senior dev sighs every time you ask about them So here's the thing. You've been writing code for a while now. Maybe a year, maybe two. You can build a REST API, you know what a database is, you've definitely Googled "how to fix CORS error" at least 47 times. You're getting there. But then someone in a meeting drops a word like idempotency or eventual consistency and suddenly everyone's nodding like they totally get it, and you're just sitting there smiling and thinking — what the hell does that mean and why did no one explain it properly. This blog is for that version of you. And honestly, a little bit for me too because I've been that person more times than I'd like to admit. 1. Idempotency (the one everyone pretends to understand) Okay so idempotency basically means — if you do the same operation multiple times, the result should be the same as doing it once. That's it. That's the whole thing. But where it actually matters is in APIs. Say a user clicks "Pay Now" and the request fails halfway.…