Building PrepWise: An AI-Powered Technical Interview Simulator using React, Node.js, and Gemini"

Ankur Yadav — Tue, 23 Jun 2026 08:16:36 +0000

🚀 The Problem: The High-Stress World of Technical Interviews

Let’s be honest: Technical interviews are stressful. You can solve countless algorithm problems, but nothing prepares you for the pressure of talking through your system design choices, debugging code in front of a live interviewer, or explaining complex concepts like React hooks lifecycle, middleware security, or database indexing, in real-time.

To bridge this gap, I built PrepWise — a complete, responsive AI-powered interview simulator that acts as your personal technical companion. It simulates actual interviewer behavior, supports multiple technical specialties, evaluates your problem-solving depth, and provides a comprehensive feedback dashboard.

Here is an in-depth look at how I designed, built, and optimized PrepWise!

🛠️ The Tech Stack

I designed PrepWise with a clean, decoupled full-stack architecture built to run quickly and cost-effectively:

Frontend: React 18, Vite, TypeScript, and Lucide React.
Styling & Animations: Tailwind CSS (for custom dark aesthetics and responsive grids) + Framer Motion (for fluid slide-ins, dynamic card expansions, and spring animations).
Backend Service: Node.js & Express API proxy layer to handle LLM communication safely without exposing API keys.
Database & Auth: Firebase Firestore (for structured, real-time persistence of historical interviews and scorecards) + Firebase Authentication (supporting secure password entries and instant Google SSO).
Core AI Intelligence: Google Gemini API SDK (@google/genai) for streaming-like conversation generation and high-precision evaluation matrices.

🏛️ System Architecture

PrepWise uses a hybrid client-server topology that prioritize user privacy, low-latency, and flexible customization:

               +-------------------------------------------------+
               |              React Frontend SPA                 |
               |  (Dashboard, Chat Workspace, Custom Settings)   |
               +-------+-------------------+---------------------+
                       |                   |
                       | [Secure APIs]     | [Real-time Sync/Auth]
                       v                   v
     +-----------------+--------+  +-------+---------------------+
     |    Node/Express Server   |  |        Cloud Firebase       |
     |                          |  |                             |
     | - /api/chat-stream       |  | - Firebase Auth             |
     | - /api/generate-insights |  | - Cloud Firestore Database  |
     +---------+----------------+  +-----------------------------+
               |
               | [API Keys Integration]
               v
     +---------+----------------+
     |     Google Gemini API    |
     | (Interviewer & Scorer)   |
     +--------------------------+

🔥 Core Engineering Achievements

1. Instant Optimistic UI Settings Save
Nothing breaks an application’s user experience like an endless loading spinner. In PrepWise, saving API keys or updating user profile names uses Optimistic UI Synchronization.
When you click save, the local React layout instantly updates, launches a custom visual confirmation Toast, and closes the settings page. Meanwhile, Firestore synchronization runs asynchronously in the background. If the background save fails, the system rolls back and notifies you gracefully.
2. Deep Analytical Scorecards
PrepWise does not just say "Good job." It analyzes performance across 4 critical vectors:
Technical Accuracy (Are you answering with code facts?)
Communication Quality (Are you explaining your thought process?)
Problem-Solving Methodology (How clean is your problem-solving structure?)
Overall Competence
The results are generated server-side using customized JSON schemas via the Gemini API, returning an extensive breakdown containing key strengths (Positives), concrete growth-areas (Improvements), and a tailored syllabus of recommended tutorials.

💬 I Need Your Feedback!

PrepWise is live, compiles perfectly, and runs on lightning-fast architectures. I would love to get your thoughts on how I can make it even better for developers.
When you try the app, I'd appreciate your feedback on:
Interviewer Behavior: Does the AI ask realistic follow-ups? Are the technical questions too easy or too hard?
Analysis Quality: Are the positive/improvement suggestions constructive and accurate?
UI/UX & Responsiveness: How does the visual layout feel on your device? Are there any minor details, spacing issues, or font improvements you would recommend?
👉 Try it here: https://prepwise-zzcq.onrender.com/
👉 Source Code: https://github.com/Ankur1079/PrepWise
Let me know your thoughts or suggestions in the comments below! 👇

DEV Community: Ankur Yadav

Building PrepWise: An AI-Powered Technical Interview Simulator using React, Node.js, and Gemini"

🚀 The Problem: The High-Stress World of Technical Interviews

🛠️ The Tech Stack

🏛️ System Architecture

🔥 Core Engineering Achievements

💬 I Need Your Feedback!