The problem with most interview prep
I've done a lot of interviews. Enough to know that reading about system design, memorizing Big-O notation, and writing out STAR stories in a Notion doc does almost nothing for your actual delivery on the day. You show up, someone asks "tell me about a time you disagreed with a technical decision," and you say "um" fourteen times and trail off into a sentence that has no ending.
The gap isn't knowledge — it's that you've never actually said the thing out loud under any kind of pressure. That's the part that most prep completely skips.
VibePi is built for exactly that gap.
What VibePi actually does
It's an AI interview coach on iOS and Android. You pick a role, get a question, speak your answer, and it gives you real feedback — not just "good job" but specific notes on filler words, pacing, confidence, content structure, and delivery. You can run as many sessions as you want.
The role-specific prep is what makes it useful for developers specifically. A "software engineer" session gives you different questions than a "product manager" session would. The content feedback knows what a strong technical answer actually looks like versus a vague one.
My actual session structure
I use it in three distinct modes depending on where I am in the prep cycle:
1. Cold run, first thing
Before I've done any prep for a specific role, I'll do a cold session. No notes, no warm-up, just answer the question like it's the real interview. The feedback from that session tells me what's actually broken — not what I think is broken. Usually it's pacing (I talk too fast when I'm nervous) and filler words ("basically" is mine). Sometimes the content feedback catches that I buried the main point three paragraphs in.
2. Targeted drilling after feedback
Once I know my weak spots, I drill those specifically. If the feedback says my answer lacked a clear outcome in the STAR structure, I'll redo the same type of question three times back to back focusing only on landing a concrete result at the end. VibePi tracks this across sessions so you can see whether you're actually improving or just repeating the same mistake with more confidence.
3. Pressure simulation the day before
The day before an interview I'll do a full session treating it exactly like the real thing — phone propped up, no pausing, no retakes. I time myself. The goal is to get comfortable with the feeling of committing to an answer even when you're not 100% sure it's perfect. That's what interviews actually require.
The feedback that surprised me most
I expected VibePi to catch filler words — that felt like the obvious use case. What I didn't expect was the content feedback being as specific as it is. It'll tell you if your answer is too abstract ("I improved the system performance") without any numbers or mechanism, or if you spent 70% of your answer on context and barely touched the actual outcome.
For behavioural questions especially, that content structure feedback is where I got the most improvement. I thought I was telling good stories. Turns out I was setting up elaborate situations and then landing on a resolution that was one sentence long.
What doesn't replace it
VibePi isn't a mock interviewer in the conversational sense — it won't follow up with "interesting, but how did you handle the edge case where X?" like a human interviewer would. For that kind of back-and-forth pressure, you still need a real person or something like lac mind set up as an adversarial model. What VibePi does is remove the excuse of "I just haven't practised saying it out loud enough." There's no reason to walk into an interview having only rehearsed in your head.
The honest assessment
The biggest thing VibePi changed for me is that I stopped treating interview prep as a reading exercise. The feedback loop — speak, get scored, adjust, repeat — is the only thing that actually moves the needle on delivery. And delivery is at least half of what an interview is.
If you're prepping for a role right now, the practical tip is this: do one cold session today before you've reviewed anything. Screenshot the feedback. That's your real baseline — not how confident you feel reading your notes.
Download it at vibepi.com — iOS and Android, free to start.