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ZachCodingInterview Logo

AI-Powered Mock Interview & Recruiter Platform

Practice coding, behavioral, system design, and resume-based interviews against a real AI interviewer - then get a full report, verdict, and PDF at the end. Recruiters can post real questions, invite real candidates, and review real results.

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🚀 What is ZachCodingInterview?

ZachCodingInterview is a full-stack mock interview platform. A candidate signs up, picks an interview type - Coding, Behavioral, System Design, Resume-Based, or Domain-Specific - dials in a seniority level and company tier, and sits a real, timed interview against an AI interviewer. Code gets executed and graded against real test cases in a sandboxed runner, and every interview ends with an AI-generated report, verdict, and downloadable PDF.

It isn't just a practice tool, though. There's a full recruiter side: recruiters apply for verified access, get approved by an admin, submit their own interview questions for review, send direct invites to candidates, and read the reports on how those candidates actually performed. An admin panel sits on top to manage users, approve recruiter applications, and moderate submitted questions.

This project is hand-built, not vibe-coded - the schema, the route architecture, the auth flows, the billing integration, and the code execution pipeline were all designed and iterated on by hand (the full history is in prisma/migrations, one deliberate change at a time).

✨ Features

Interview Engine

  • 5 interview types: Coding, Behavioral, System Design, Resume-Based, Domain-Specific
  • Seniority-aware (Entry → Principal) and company-tier-aware (Startup / Mid-Market / FAANG) question generation
  • Live, timed sessions with a per-interview time limit
  • AI-generated final report with strengths, weaknesses, suggestions, and a hire/no-hire style verdict

Code Execution

  • Real test cases run against a sandboxed execution service (JavaScript & Python)
  • Pass / fail / runtime error / time-limit-exceeded verdicts per test case
  • Language-aware test harness that wraps candidate submissions before execution

Practice Mode

  • Standalone LeetCode-style practice bank, separate from full mock interviews
  • Public, hidden, and custom test case visibility per question
  • Built-in hints per question

Resume Tools

  • Upload a resume → parsed automatically → AI-generated resume feedback (ATS score, strengths, weaknesses, suggestions)
  • Resume content can feed directly into resume-based interview questions
  • Resumes are scanned through VirusTotal before they're ever trusted

Recruiter Workspace

  • Apply for recruiter access → admin review → approve/reject
  • Submit original interview questions for approval
  • Send direct interview invites to any candidate by email
  • Review candidate reports and make hire decisions

Admin Dashboard

  • Manage users and roles
  • Approve or reject recruiter applications
  • Approve or reject community-submitted questions

Auth & Billing

  • Email/password + GitHub OAuth + Google OAuth via Better Auth
  • Forgot / reset password flows
  • Free and Pro tiers via Polar, with in-app upgrade prompts and subscription-aware gating

Reports & Storage

  • Interview reports and resume feedback rendered to PDF (@react-pdf/renderer)
  • Files stored in Vercel Blob
  • Rate limiting on sensitive endpoints

🏗️ Architecture

graph TD
    UI[Next.js Frontend<br/>App Router + React 19]

    subgraph RouteGroups [Role-Based Route Groups]
        Auth["(auth)<br/>signin · signup · reset"]
        Dashboard["(dashboard)<br/>candidate space"]
        Recruiter["(recruiter)<br/>recruiter space"]
        Admin["(admin)<br/>admin space"]
        Suspended["(suspended)"]
    end

    API[tRPC Routers + Better Auth API]

    subgraph Features [Feature Server Logic]
        FDash[features/dashboard]
        FRec[features/recruiters]
        FAdmin[features/admin]
        FAuth[features/auth]
    end

    subgraph Helpers [Core Helpers]
        AI[ai.ts<br/>Gemini prompting + fallback]
        Code[codeExecution.ts + testHarness.ts]
        Report[reportGeneration.ts + reportPdf.ts]
        Resume[resumeFeedback.ts + pdfExtract.ts]
        Malware[malwareScan.ts]
        Mail[mail.ts]
    end

    DB[(PostgreSQL<br/>via Prisma)]
    Gemini[Gemini API<br/>questions · feedback · reports]
    Sandbox[Code Execution Sandbox<br/>zachcodinginterview_codeserver]
    VT[VirusTotal API]
    Blob[Vercel Blob<br/>resumes + report PDFs]
    BetterAuth[Better Auth<br/>email · GitHub · Google]
    PolarSvc[Polar<br/>subscriptions + checkout]
    SMTP[Nodemailer<br/>transactional email]

    UI --> Auth & Dashboard & Recruiter & Admin & Suspended
    Auth & Dashboard & Recruiter & Admin --> API
    API --> FDash & FRec & FAdmin & FAuth
    FDash & FRec & FAdmin --> AI & Code & Report & Resume & Malware & Mail
    FAuth --> BetterAuth

    AI --> Gemini
    Code --> Sandbox
    Malware --> VT
    Resume --> Blob
    Report --> Blob
    Mail --> SMTP
    API --> PolarSvc

    AI & Code & Report & Resume & Malware --> DB
    BetterAuth --> DB
    PolarSvc --> DB

    classDef ui fill:#f9f9f9,stroke:#d1d5db,color:#000
    classDef route fill:#eff6ff,stroke:#bfdbfe,color:#1e3a8a
    classDef api fill:#f9fafb,stroke:#e5e7eb,color:#000
    classDef feature fill:#eef2ff,stroke:#c7d2fe,color:#3730a3
    classDef helper fill:#ecfdf5,stroke:#a7f3d0,color:#065f46
    classDef external fill:#fef3c7,stroke:#fde68a,color:#92400e
    classDef db fill:#fff1f2,stroke:#fecdd3,color:#9f1239

    class UI ui
    class Auth,Dashboard,Recruiter,Admin,Suspended route
    class API api
    class FDash,FRec,FAdmin,FAuth feature
    class AI,Code,Report,Resume,Malware,Mail helper
    class Gemini,Sandbox,VT,Blob,BetterAuth,PolarSvc,SMTP external
    class DB db
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🔄 How an Interview Works

graph LR
    Step1[1. Pick Type<br/>Coding · Behavioral · System Design<br/>Resume-Based · Domain-Specific]
    Step2[2. Set Difficulty<br/>Seniority + company tier]
    Step3[3. AI Generates Questions<br/>Gemini, seniority-aware]
    Step4[4. Candidate Attempts<br/>Code runs in sandbox / answers recorded]
    Step5[5. Grading<br/>Test cases + AI evaluation]
    Step6[6. Report Generated<br/>Verdict, strengths, weaknesses, PDF]
    Step7[7. Recruiter Review<br/>if invited by a recruiter]

    Step1 --> Step2
    Step2 --> Step3
    Step3 --> Step4
    Step4 --> Step5
    Step5 --> Step6
    Step6 --> Step7

    classDef s1 fill:#eff6ff,stroke:#bfdbfe,color:#1e3a8a
    classDef s2 fill:#eef2ff,stroke:#c7d2fe,color:#3730a3
    classDef s3 fill:#fff1f2,stroke:#fecdd3,color:#9f1239
    classDef s4 fill:#fef3c7,stroke:#fde68a,color:#92400e
    classDef s5 fill:#fdf4ff,stroke:#f3e8ff,color:#6b21a8
    classDef s6 fill:#ecfdf5,stroke:#a7f3d0,color:#065f46
    classDef s7 fill:#f0fdf4,stroke:#bbf7d0,color:#166534

    class Step1 s1
    class Step2 s2
    class Step3 s3
    class Step4 s4
    class Step5 s5
    class Step6 s6
    class Step7 s7
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🗃️ Data Model

erDiagram
    User ||--o{ Interview : "takes (candidate)"
    User ||--o{ Interview : "assigns (recruiter)"
    User ||--o{ PracticeAttempt : attempts
    User ||--o| Resume : uploads
    User ||--o| RecruiterApplication : submits
    User ||--o{ RecruiterApplication : reviews
    User ||--o{ Question : creates
    User ||--o{ Question : reviews
    User ||--o{ RecruiterInvite : sends
    User ||--o{ RecruiterInvite : receives
    User ||--o| Settings : has
    User ||--o{ Session : has
    User ||--o{ Account : has

    Interview ||--o{ InterviewQuestion : contains
    Interview ||--o| Report : generates
    Interview ||--o| RecruiterInvite : "fulfills"

    Question ||--o{ TestCase : has
    Question ||--o{ InterviewQuestion : "used in"
    Question ||--o{ PracticeAttempt : "practiced via"

    Resume ||--o| ResumeFeedback : generates
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🛠️ Tech Stack

Layer Technology
Frontend Next.js 16 (App Router), React 19, TypeScript, Tailwind CSS v4
Components shadcn/ui, Radix UI, Monaco Editor
API tRPC v11, TanStack Query
Database PostgreSQL, Prisma ORM
Auth Better Auth, GitHub OAuth, Google OAuth
AI Google Gemini via Vercel AI SDK (@ai-sdk/google, ai)
Code Execution Custom sandbox - zachcodinginterview_codeserver
File Storage Vercel Blob
Malware Scanning VirusTotal API
Billing Polar
Email Nodemailer
PDF Generation @react-pdf/renderer
Linting Biome

🚀 Quick Start

Clone the repository

git clone https://github.com/19akshansh/zachcodinginterview.git
cd zachcodinginterview

Install dependencies

npm install

Configure environment variables

Copy the example file and fill in your own values:

cp example.env .env

See Environment Variables below for what each one does.

Set up the database

npm run db:generate
npm run db:migrate

Start the development server

npm run dev

Other useful scripts

npm run build       # production build
npm run lint         # biome check
npm run format        # biome format --write
npm run db:studio     # open Prisma Studio
npm run db:reset      # reset the database

🔑 Environment Variables

All variables are documented in example.env. Copy it to .env and fill in your own values.

Variable Description Required
NEXT_PUBLIC_APP_URL Public URL of your deployment Yes
DATABASE_URL PostgreSQL connection string Yes
BETTER_AUTH_SECRET Secret key for Better Auth sessions Yes
BETTER_AUTH_URL Base URL for auth callbacks Yes
GITHUB_CLIENT_ID / GITHUB_CLIENT_SECRET GitHub OAuth No (for GitHub sign-in)
GOOGLE_CLIENT_ID / GOOGLE_CLIENT_SECRET Google OAuth No (for Google sign-in)
EMAIL_USER / EMAIL_PASS / EMAIL_FROM Nodemailer transactional email (verification, invites, etc.) Yes
POLAR_ACCESS_TOKEN / POLAR_SERVER Polar API access token and environment (sandbox or production) Yes
NEXT_PUBLIC_POLAR_PRO_PRODUCT_ID / POLAR_PRO_PRODUCT_ID Polar Pro product ID Yes
POLAR_SUCCESS_URL Redirect URL after a successful checkout Yes
CODESERVER_API_URL / CODESERVER_APIKEY / CODESERVER_TIMEOUT_MS The code execution sandbox - see shout-out below Yes (for code execution)
BLOB_READ_WRITE_TOKEN Vercel Blob storage for resumes & report PDFs Yes
GEMINI_API_KEY Fallback AI key - as of v0.9.6 users can bring their own key in-app No
VIRUSTOTAL_API_KEY / VIRUSTOTAL_BASE Malware scanning for uploaded resumes Yes

📂 Project Structure

zachcodinginterview/
├── prisma/
│   ├── schema.prisma        # 15 models: User, Interview, Question, Report, Resume...
│   └── migrations/          # full migration history - this schema evolved over time
├── public/
│   └── mainAssets/
│       ├── logo.svg
│       └── logoFull.svg     # the logo at the top of this README
├── src/
│   ├── app/                  # Next.js App Router - grouped by access level
│   │   ├── (auth)/           # signin, signup, forgot/reset password
│   │   ├── (dashboard)/      # candidate space: interviews, practice, resume, reports, profile
│   │   ├── (recruiter)/      # recruiter space: review, invites, question submissions
│   │   ├── (admin)/          # admin space: users, applications, question moderation
│   │   ├── (suspended)/      # shown to suspended/banned accounts
│   │   └── api/              # tRPC + Better Auth route handlers
│   ├── features/              # feature-sliced UI + server logic, mirrors the app/ groups
│   │   ├── dashboard/           # interviews, practice, resume, reports, settings, submissions
│   │   ├── recruiters/
│   │   ├── admin/
│   │   └── auth/
│   ├── components/
│   │   ├── ui/                  # shadcn/ui primitives
│   │   └── layout/               # navbars, sidebars, shells
│   ├── helpers/                   # framework-agnostic business logic
│   │   ├── ai.ts                    # Gemini prompting, retries, fallback models
│   │   ├── codeExecution.ts          # talks to the code execution sandbox
│   │   ├── testHarness.ts            # wraps candidate code for each language
│   │   ├── reportGeneration.ts       # builds the final interview report
│   │   ├── reportPdf.ts / pdfTemplate.tsx
│   │   ├── resumeFeedback.ts / pdfExtract.ts
│   │   ├── malwareScan.ts            # VirusTotal integration for uploads
│   │   └── mail.ts / storage.ts / rateLimit.ts
│   ├── lib/
│   │   ├── auth/                     # Better Auth client/server config
│   │   ├── billing/                  # Polar client + subscription helpers
│   │   └── db/                       # Prisma client singleton
│   ├── trpc/                          # tRPC router setup, client & server helpers
│   ├── config/                        # enums, constants, and validated env schema
│   └── hooks/                         # shared React hooks (subscription, breadcrumbs, gemini key...)
├── example.env                       # copy to .env and fill in
└── package.json

🖥️ Code Execution - Powered by zachcodinginterview_codeserver

Every coding interview and practice submission is executed by zachcodinginterview_codeserver - a small, dedicated sandbox service that runs candidate JavaScript/Python snippets and returns stdout, stderr, exit code, and timeout info. This app talks to it purely over HTTP via CODESERVER_API_URL + CODESERVER_APIKEY, so the sandbox can be deployed and scaled completely independently of the main app.

If you need a lightweight, self-hosted code runner for a similar project, go check it out - huge shout-out to it for making the whole coding-interview experience possible.

🗺️ Roadmap (future plans)

  • Additional executable languages beyond JavaScript & Python (Java, C++, Go, Rust are already modeled, just not wired to the sandbox yet)
  • Live video/voice mock interviews
  • Team / organization workspaces for recruiters
  • Public question bank contributions from the community
  • Richer analytics on candidate performance over time

🤝 Contributing

Contributions are welcome.

  1. Fork the repository
  2. Create a new branch (git checkout -b feat/my-feature)
  3. Commit your changes
  4. Open a pull request

📜 License

Licensed under the MIT License.

Built with Next.js, Prisma, tRPC, and Better Auth

If ZachCodingInterview helps you, consider giving the repo a ⭐

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An AI Powered Tech Interview Platform made with NextJS

zachcodinginterview.vercel.app

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