Projects/Blue-Green Deployment Platform

ProjectsCI/CD & GitOpsadvancedCI/CD

Blue-Green Deployment Platform

Traffic switching, health checks and rollback.

~16 hours 8 phases

DockerNginxLinuxCI/CD

Overview

Implement a blue-green deployment platform with two live environments, traffic switching, health checks and instant rollback.

The problem

Deploy with zero downtime by switching traffic between blue and green environments.

Why it matters

This is a real, in-demand scenario: Deploy with zero downtime by switching traffic between blue and green environments.. Teams that can ship and run a ci/cd like this solve an actual business need and are hired for that ability.

What you'll build

A blue-green setup
Automated switch
Rollback

What you'll learn

Zero-downtime deploys
Traffic management

Business problem

Deployments must not interrupt users.

Technical problem

Run parallel environments and switch traffic with rollback.

When you're done: A working ci/cd project — code committed, tests passing, and documented in your portfolio.

Requirements

User requirements

Zero-downtime deploys
Health-gated switch
Instant rollback

System requirements

Two environments
Router
Health checks

Functional requirements

Blue/green environments
Health check
Traffic switch
Rollback

Non-functional requirements

Atomic switch
Observable

Technical requirements

Nginx upstreams
health endpoints

Security requirements

Validate health before switch

Operational requirements

Documented switch script

Constraints

Docker + Nginx

Success criteria

Switch is seamless
Rollback is instant

Flows

Request Flow

1
Browser
User requests the application over HTTPS.
2
CDN / DNS
Edge routes the request to the origin.
3
Load Balancer
Distributes traffic across healthy app instances.
4
Application
Handles the request, applies business logic.
5
Cache
Serves fast reads for hot data.
6
Database
Persists data and returns results.

Project Structure

src

Root of the client application source.

Setup

1
Prerequisites
You need the tools required by Docker, Nginx, Linux installed and available on your PATH.
2
Clone project
Clone the repository locally.
1. Clone the repository
git clone <your-repo-url> <project-folder>
3
Install dependencies
Install the project dependencies.
1. Initialize a Node.js project
Linux / Windows
npm init -y
Expected
Creates a package.json with defaults.
If it fails
command not found: npm
Fix
Install Node.js LTS from the official site, then reopen your terminal.
4
Configure environment
Set the environment variables documented for this project. Never commit secrets.
1. Create the environment file
cp .env.example .env # then edit values
5
Start project
Run the development command and confirm it starts.
1. Start the development server
Linux / Windows
npm run dev
Expected
Dev server starts; watch terminal for the local URL.
If it fails
Port 3000 is already in use
Fix
Run on another port: npm run dev -- --port 3001, or stop the conflicting process.
6
Verify
Open the printed local URL and confirm the primary flow works.

Build Phases

0 of 8 phases complete

Objective: Establish the next milestone of the delivery pipeline.
What changes: The project advances to the next coherent state, keeping the previous milestones working.
Files touched
Relevant source and configuration files for this milestone.
Run
1. Initialize a Node.js project
Linux / Windows
npm init -y
Expected
Creates a package.json with defaults.
If it fails
command not found: npm
Fix
Install Node.js LTS from the official site, then reopen your terminal.
Tasks
- Implement the specific behaviour required for this milestone.
- Verify the previous milestone still works.
Validate: The milestone behaves as expected and does not break existing functionality.
Common mistakes
- • Skipping validation and moving on before confirming the milestone works.
Objective: Establish the next milestone of the delivery pipeline.
What changes: The project advances to the next coherent state, keeping the previous milestones working.
Files touched
Relevant source and configuration files for this milestone.
Run
1. Install the docker package
Linux / Windows
npm install docker
Expected
Adds docker to node_modules and package.json.
If it fails
npm ERR! network / EACCES
Fix
Check your network or run with sudo on Linux/macOS; on Windows run the terminal as Administrator.
Tasks
- Implement the specific behaviour required for this milestone.
- Verify the previous milestone still works.
Validate: The milestone behaves as expected and does not break existing functionality.
Common mistakes
- • Skipping validation and moving on before confirming the milestone works.
Objective: Establish the next milestone of the delivery pipeline.
What changes: The project advances to the next coherent state, keeping the previous milestones working.
Files touched
Relevant source and configuration files for this milestone.
Run
1. Start the development server
Linux / Windows
npm run dev
Expected
Dev server starts; watch terminal for the local URL.
If it fails
Port 3000 is already in use
Fix
Run on another port: npm run dev -- --port 3001, or stop the conflicting process.
Tasks
- Implement the specific behaviour required for this milestone.
- Verify the previous milestone still works.
Validate: The milestone behaves as expected and does not break existing functionality.
Common mistakes
- • Skipping validation and moving on before confirming the milestone works.
Objective: Establish the next milestone of the delivery pipeline.
What changes: The project advances to the next coherent state, keeping the previous milestones working.
Files touched
Relevant source and configuration files for this milestone.
Run
1. Build the application for production
Linux / Windows
npm run build
Expected
A production bundle is emitted to the output directory.
If it fails
Build fails with a type or syntax error
Fix
Read the error message, fix the referenced file, and re-run the build.
Tasks
- Implement the specific behaviour required for this milestone.
- Verify the previous milestone still works.
Validate: The milestone behaves as expected and does not break existing functionality.
Common mistakes
- • Skipping validation and moving on before confirming the milestone works.
Objective: Establish the next milestone of the delivery pipeline.
What changes: The project advances to the next coherent state, keeping the previous milestones working.
Files touched
Relevant source and configuration files for this milestone.
Tasks
- Implement the specific behaviour required for this milestone.
- Verify the previous milestone still works.
Validate: The milestone behaves as expected and does not break existing functionality.
Common mistakes
- • Skipping validation and moving on before confirming the milestone works.
Objective: Establish the next milestone of the delivery pipeline.
What changes: The project advances to the next coherent state, keeping the previous milestones working.
Files touched
Relevant source and configuration files for this milestone.
Tasks
- Implement the specific behaviour required for this milestone.
- Verify the previous milestone still works.
Validate: The milestone behaves as expected and does not break existing functionality.
Common mistakes
- • Skipping validation and moving on before confirming the milestone works.
Objective: Establish the next milestone of the delivery pipeline.
What changes: The project advances to the next coherent state, keeping the previous milestones working.
Files touched
Relevant source and configuration files for this milestone.
Tasks
- Implement the specific behaviour required for this milestone.
- Verify the previous milestone still works.
Validate: The milestone behaves as expected and does not break existing functionality.
Common mistakes
- • Skipping validation and moving on before confirming the milestone works.
Objective: Establish the next milestone of the delivery pipeline.
What changes: The project advances to the next coherent state, keeping the previous milestones working.
Files touched
Relevant source and configuration files for this milestone.
Tasks
- Implement the specific behaviour required for this milestone.
- Verify the previous milestone still works.
Validate: The milestone behaves as expected and does not break existing functionality.
Common mistakes
- • Skipping validation and moving on before confirming the milestone works.

Commands

1. Initialize a Node.js project

Linux / Windows

npm init -y

Expected

Creates a package.json with defaults.

If it fails

command not found: npm

Fix

Install Node.js LTS from the official site, then reopen your terminal.

2. Install the docker package

Linux / Windows

npm install docker

Expected

Adds docker to node_modules and package.json.

If it fails

npm ERR! network / EACCES

Fix

Check your network or run with sudo on Linux/macOS; on Windows run the terminal as Administrator.

3. Start the development server

Linux / Windows

npm run dev

Expected

Dev server starts; watch terminal for the local URL.

If it fails

Port 3000 is already in use

Fix

Run on another port: npm run dev -- --port 3001, or stop the conflicting process.

4. Build the application for production

Linux / Windows

npm run build

Expected

A production bundle is emitted to the output directory.

If it fails

Build fails with a type or syntax error

Fix

Read the error message, fix the referenced file, and re-run the build.

Testing

Unit tests

Core logic and pure functions behave correctly.
npm init -y
Success: All unit tests pass without errors.

Integration tests

Components integrate correctly with data sources and services.
npm test
Success: Integration tests pass for the primary flows.

API tests

Endpoints respond to valid and invalid input correctly.
npm test
Success: API tests cover happy and failure paths.

End-to-end tests

A user can complete the primary journey end to end.
npm run test:e2e
Success: The main user journey completes successfully.

Security tests

No obvious security regressions are introduced.
npm audit
Success: No high or critical vulnerabilities.

Debugging & Troubleshooting

Port already in use at startup

Why: Another process is binding the same port your app wants.

Check: List what is using the port.

lsof -i :3000   # Linux/macOS  |  netstat -ano | findstr :3000   # Windows

Fix: Free the port or start your app on a different port.

Prevent: Choose uncommon ports and document them in the README.

Environment variable missing or undefined

Why: A required value was not loaded into the runtime.

Check: Print the variable or inspect the config loader.

echo $MY_VAR   # Linux/macOS  |  echo %MY_VAR%   # Windows

Fix: Add the variable to your .env file and restart the process.

Prevent: Fail fast at startup when required env vars are absent.

API request times out

Why: An upstream call is slow or the network is blocked.

Check: Time a direct request against the upstream.

curl -w 'time_total: %{time_total}\n' http://upstream/health

Fix: Add timeouts and retries to the client; verify the upstream is up.

Prevent: Set explicit timeouts and circuit breakers on outbound calls.

Dependency fails to install or run

Why: Version conflicts or an incompatible runtime.

Check: Inspect the error and the installed versions.

npm ls <pkg>

Fix: Align versions or clear the lockfile and reinstall.

Prevent: Commit a lockfile and use the same Node version everywhere.

Security

Security is treated as a core requirement: input is validated, secrets are protected, and dependencies are kept up to date.

Input validation
Validate and sanitize all user input before use.
Secrets management
Store secrets in environment variables, never in source.
Dependency hygiene
Regularly audit dependencies for known vulnerabilities.

Observability

Logs

Structured logs for every service
Centralized log storage with retention

Metrics

Service, infrastructure and business metrics
RED and USE coverage

Traces

Distributed traces across services and infrastructure

Health checks

Per-service health probes
External uptime checks

Alerts

Alerting on SLO burn and critical signals
On-call escalation paths

Dashboards

Service, infra and business dashboards
SLO dashboards

SLIs

Availability — Proportion of valid requests answered successfully
Latency — Distribution of response times
Error rate — Proportion of failed requests

SLOs

Availability — 99.9% over 30 days
Latency — P95 under 300ms

Deployment

1
Prepare for deployment
Build the production artifact.
1. Build for production
npm run build
2
Deploy
Deploy to the project target platform following its documented steps.
1. Deploy
npm run deploy # or the platform-specific command
3
Verify
Confirm the deployed application responds and its health check passes.
1. Check health
curl -I https://<your-deployed-url>

Documentation

Project Overview

Implement a blue-green deployment platform with two live environments, traffic switching, health checks and instant rollback. This is a advanced ci/cd project in the delivery pipeline space, built to demonstrate real engineering, not just copied code.

What You Will Build

- A blue-green setup - Automated switch - Rollback

Problem Statement

Deployments must not interrupt users. Run parallel environments and switch traffic with rollback.

Technology Stack

Docker, Nginx, Linux, CI/CD

Installation

Clone the repository and install dependencies with the documented commands.

Local Development

Run the development command and open the printed local URL.

Testing

Run the test commands documented in the Testing section and confirm they pass.

Deployment

Follow the documented deployment steps for this project's target platform.

Interview Explanation

Use the Interview section to explain the architecture, technology choices and trade-offs.

Build Process

Phases guide the build in 8 checkpoints. Complete each and validate before moving on.

Interview Prep

30-second pitch

I built Blue-Green Deployment Platform — deploy with zero downtime by switching traffic between blue and green environments. It uses Docker, Nginx, Linux and solves deployments must not interrupt users.

2-minute walkthrough

Implement a blue-green deployment platform with two live environments, traffic switching, health checks and instant rollback. The core requirements were Blue/green environments, Health check, Traffic switch. I structured the work around Design blue-green, Switch traffic safely, Automate rollback and validated the result with the documented tests.

Architecture

The architecture is described by the interactive diagram in the Architecture section, which maps the request and deployment flows.

Why these technologies

I chose Docker, Nginx, Linux, CI/CD because they are the pragmatic, well-supported tools best suited to building a ci/cd of this kind.

Why this architecture

The structure exists to keep concerns separated, make each piece testable, and scale the project cleanly as requirements grow.

At scale

At scale I would introduce caching, move to a service boundary structure, add proper observability, and enforce stricter contracts between components.

What can fail

The data source becomes unavailable, A dependency introduces a breaking change, Performance degrades under load, Configuration drift between environments

Monitoring

Monitoring is covered in the Observability section, focusing on distributed metrics, logs, traces and SLOs.

Security

Security was handled by validating input, protecting secrets, and following the practices listed in the Security section.

Deployment strategy

Deployment follows the steps in the Deployment section for the target platform, with a health check to confirm success.

What I'd do differently

With more time I would add deeper test coverage, stronger observability, and automated deployment.

Practice Q&A

Why did you build Blue-Green Deployment Platform?

To demonstrate Design blue-green and Switch traffic safely on a real, portfolio-worthy project.

What was the hardest part?

Coordinating the pieces so each stays correct as the project grows, and validating end to end.

How do you handle failure and scale?

By designing explicit failure handling and scale considerations into the architecture.

Extensions

Add deeper test coverage
Add observability and alerting
Harden security
Automate deployment

Completion Checklist

Prerequisite Projects

Next Steps

Recommended next

Canary Deployment Platform

Progressive delivery refines the same idea.