From Zero to Deployment: Dockerizing a Flask + PostgreSQL App on AWS

Tanay Jain — Sun, 29 Mar 2026 18:56:16 +0000

When I started learning Docker, I had no idea I’d end up deploying a real application on a cloud server within the same month.

It ended up changing how I think about building software.

The Idea

I didn’t want to build just another static project.

I wanted:

A real backend
A real database
A real deployment

So I built a simple web app that tracks page visits and stores them in PostgreSQL.

Tech Stack

Python Flask (backend)
PostgreSQL (database)
Docker & Docker Compose
AWS EC2 (deployment)

Architecture

User (Internet)
   ↓
AWS EC2 Server
   ↓
Docker Engine
   ↓
Flask Container (Port 80)
   ↓ psycopg2
PostgreSQL Container
   ↓
Persistent Volume (pgdata)

Key Concepts I Implemented

🔹 Multi-container system

Instead of running containers manually, I used Docker Compose.

docker compose up -d

This starts the entire system in one command.

🔹 Environment variables (.env)

No secrets inside the code.

Cleaner
Safer
Production-ready

🔹 Health checks

Docker monitors the application continuously.

If Flask stops responding, the container is marked as unhealthy.

🔹 Auto-restart

Using:

restart: always

If a container crashes, Docker automatically restarts it.

🔹 Optimized Dockerfile

Used python:3.10-slim
Cleared apt cache after install
Used --no-cache-dir for pip
Optimized layer ordering

Result: Image size reduced significantly (~300MB → ~160MB)

Biggest Challenge

Connecting Flask to PostgreSQL inside Docker.

The key realization:

Containers communicate using service names, not IP addresses.

DB_HOST=db

Docker internally resolves db to the PostgreSQL container.

Once this clicked, the setup became much clearer.

Deployment

I deployed the app on AWS EC2.

Steps:

Launch EC2 instance
Install Docker
Clone project
Run Docker Compose

The application was then accessible via a public IP.

What I Learned

Docker is not just about containers.

It’s about building systems that are:

Reproducible
Isolated
Self-healing
Easy to deploy

Final Thoughts

This project was my first real experience combining backend, database, and deployment into one system.

If you're learning Docker, building and deploying even a small project like this gives much more clarity than just following tutorials.

DEV Community: Tanay Jain