Pesapal Junior Dev Challenge ’26 – Custom RDBMS Playground

This repository contains my submission for the Pesapal Junior Developer Challenge 2026. It demonstrates a lightweight relational database management system (RDBMS) built from scratch, with a web interface for CRUD operations.

Both backend and frontend live in the same repository for ease of execution and review.

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Challenge Overview

The goal of this challenge was to:

• Design and implement a simple RDBMS

• Support:

  • Table creation with data types
  • Primary keys and unique constraints
  • Basic CRUD operations
  • Indexing
  • Joins (basic)

• Include an interactive REPL

• Build a web app demonstrating database CRUD

Backend – RDBMS & API

Features

• In-memory relational tables

• Supported data types:

  • INT – integer values
  • STR – string values

• Primary keys

• Auto-incrementing IDs

• CRUD operations via REST API:

  • Create (POST)
  • Read (GET)
  • Update (PUT / PATCH)
  • Delete (DELETE)

• JSON persistence for tables (<table_name>_table.json)

Why FastAPI?

I chose FastAPI because:

• Lightweight and fast
• Built-in validation via Pydantic
• Auto-generated interactive documentation
• Easy integration with JSON-based RDBMS
• Allows me to focus on database logic

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Run Backend

1. Create a Python virtual environment:

git clone https://github.com/mutungapeter/Custom-RDMS.git
cd Custom-RDMS
python -m venv venv
source venv/bin/activate      
cd backend
pip install -r requirements.txt

2. Start FastAPI server:

uvicorn api.main:app --reload

3. API will be available at:

http://127.0.0.1:8000/docs/

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API Endpoints

Tables

Method	Endpoint	Description
POST	/tables/{name}	Create a table
DELETE	/tables/{name}	Delete a table

Records

Method	Endpoint	Description
GET	/tables/{name}/records	List all records in table
POST	/tables/{name}/records	Insert new record(s)
PUT	/tables/{name}/records/{id}	Replace entire record
PATCH	/tables/{name}/records/{id}	Update specific fields
DELETE	/tables/{name}/records/{id}	Delete a record

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Interactive REPL

The RDBMS includes a REPL for direct database interaction.

Run REPL

cd backend
python -m db_engine.repl

Example Commands

> CREATE TABLE users
> INSERT INTO users name=John
> INSERT INTO users name=Mary
> SELECT * FROM users
> UPDATE users SET name=Jane WHERE id=1
> DELETE FROM users WHERE id=2

The REPL shows real-time table manipulation without the frontend.

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##Frontend – React Web App

The frontend demonstrates CRUD operations using the RDBMS API:

• Table creation & selection
• Record creation
• Record editing (PUT / PATCH)
• Record deletion
• Live updates from backend

Built using:

• React + TypeScript
• Vite (fast dev server)
• Tailwind CSS for styling

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Run Frontend

1. Install dependencies:

cd frontend
npm install

2. Start development server:

npm run dev

3. Access the app at:

http://localhost:5173

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Example Workflow

1. Create or select a table from the UI
2. Insert records (auto-increment IDs)
3. View records in the table
4. Update records using PUT / PATCH
5. Delete records
6. All changes are persisted in JSON files on backend

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AI Usage

AI tools were used for:

• Refactoring code
• Debugging minor issues

All database design, integration, and frontend logic were implemented and fully understood by me.

Built for the Pesapal Junior Developer Challenge ’26 By: Peter Sikuku