I built my own interview prep app because the ones out there weren't built for people like us

I was prepping for interviews and speaking events and tech talks while working full time, putting three kids to bed every night, and showing up to my current job like everything was fine. The apps out there were either $40 a month or missing half the things I actually needed to practice. So I did what I do. I built my own.

Here's the thing right, when you're doing interview prep with a job and kids, you don't have the luxury of grinding LeetCode for four hours on a Saturday. You've got like — maybe 45 minutes after bedtime before your brain stops working. So every minute has to count, and every tool you're using has to be actually built for that reality.

The existing apps weren't. They had the problems but not the system. No spaced repetition, so I'd solve something, feel good about it, and forget it completely two weeks later. No system design practice that was actually interactive — just walls of text I was supposed to read and somehow absorb. No way to talk through a behavioral question out loud and actually practice how I sound when I'm nervous. Just grind and hope.

So I built Elevar. 105 LeetCode problems with a Monaco code editor right in the browser, a spaced repetition engine using the SM-2 algorithm so the problems I keep getting wrong come back more often, a system design module with an Excalidraw whiteboard so I can actually sketch things out, behavioral interview prep, and voice input so I can practice talking through my answers. All local-first, runs in the browser, no account needed, no $40 a month.

The thing I keep coming back to is this — I was the target customer. I knew the problem from the inside. I knew exactly what was missing because I was the one who needed it. That's not a bad place to start building from. That's actually the best place.

And I know some people will read this and think "okay but I can't build my own app" — and that's fine, Elevar is for you too, I'll share it. But what I want you to take from this is the principle. If the tool you need doesn't exist yet, and you have enough skill to make something rough and useful, that rough useful thing is worth building. It doesn't have to be polished. It just has to work for you, and maybe for some other people who have the same problem you do.

I wrote a lot of Elevar at 11pm. Kids asleep, coffee going cold, interview at a company I actually wanted to work at on the calendar. The app is real and so was the pressure. That combination makes you ship.

Excalidraw. I use this for everything before I touch a single line of code — I drew the architecture for Elevar in Excalidraw before I wrote any of it. It's a free whiteboard tool that lives in your browser, hand-drawn aesthetic so it doesn't look precious, and you can share boards with a link. For system design practice specifically it's perfect because you're forced to think spatially about how the pieces connect.

It's also just good for thinking out loud when you don't want the overhead of a real diagramming tool. I open it the same way I open a notes app. Boxes, arrows, a few labels — done. If your plan can't survive being drawn on a whiteboard, it's not ready to be code yet.

Reply and tell me: what tool do you wish existed that you haven't been able to find? I'm genuinely curious — and I might already be building it.

Yesenia M. Perez Lead Backend Engineer. Mom of 3. Building at 11pm.

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