0. Migration Overview

This migration was not a simple frontend switch.

It was a full production architecture upgrade, including:

Data Layer

1. EC2 local file system → S3 (gp-fileserver)

2. EC2 MySQL (gp_sales_prod) → ECS-hosted DB (crm-db)

Application Layer Refactoring

3. PHP monolith backend (main site + console + FX updater)

   → consolidated into ECS: crm-backend

4. Console frontend (PHP-rendered pages)

   → extracted CRUD-only interface → ECS: crm-web

5. Next.js main site frontend

   → new independent service ECS: gp-web

Traffic Layer

6. ALB + Target Groups

7. ACM certificate issuance

8. Cloudflare DNS cutover

9. Gradual EC2 decommission

This was a layered migration across:

Storage
Database
Backend
Frontend
Network
TLS
DNS

1. Storage Migration: EC2 → S3

Objective

Decouple file storage from compute instance.

Steps

1. Identified static and uploaded files in EC2

2. Synced to S3 bucket:

S3: gp-fileserver

3. Updated backend file reference logic:

   • Replace local disk path

   • Store S3 object key

4. Tested file upload & retrieval

Key Design Principle

• Storage must be stateless

• Application containers should not depend on local disk

2. Database Migration: EC2 → ECS DB (crm-db)

Objective

Separate DB from legacy EC2 and prepare for containerized architecture.

Steps

1. Dump production DB:

mysqldump gp_sales_prod > dump.sql

2. Import into ECS-hosted MySQL container:

mysql -h <crm-db-host> < dump.sql

3. Resolve collation conflicts:

   • utf8mb4_0900_ai_ci vs utf8mb4_general_ci

4. Update application DB connection configs

Lesson

DB migration issues are rarely infrastructure problems;

they are almost always:

• Collation mismatch

• Foreign key constraints

• Charset differences

3. Backend Refactor: PHP Monolith → crm-backend

Legacy structure:

gp_sales_prod (PHP)
- Main site backend
- Admin backend
- FX updater

Refactored into:

ECS: crm-backend

Refactoring Goals

• Separate business logic from view layer

• Remove filesystem dependency

• Centralize DB access

• Prepare for future Java migration

4. Admin Frontend Simplification → crm-web

Legacy admin frontend was mixed with backend.

Refactored into:

ECS: crm-web

Scope reduced to:

• News CRUD

• FX CRUD

• Minimal admin UI

Key principle:

Reduce surface area before migration.

5. New Service: Next.js → ECS: gp-web

This was the most complex part.

New Service Required:

• New ECS Task Definition

• New ECS Service

• New Target Group (IP mode)

• ALB Listener configuration

• ACM certificate

• Cloudflare DNS update

6. Network Architecture (Final State)

User
  ↓
Cloudflare DNS
  ↓
ALB (Internet-facing)
  ↓
Target Group (IP mode, HTTP:3000)
  ↓
ECS gp-web

7. Infrastructure Components Created

7.1 ALB

• Scheme: Internet-facing

• Listener:

  • HTTPS:443

• ACM certificate bound

7.2 Target Group

• Target type: IP (Fargate requirement)

• Port: 3000

• Health check: /

• Success codes: 200-399

7.3 ECS

Task Definition:

• Container port: 3000

• Host binding: 0.0.0.0

Service:

• Desired count: 1

• Deployment strategy:

  • Minimum healthy percent = 100

  • Maximum percent = 200

8. Major Debugging Phases

This migration included layered debugging.

Phase 1: Timeout

Cause:

• ALB Security Group missing 443

Fix:

HTTPS 443 → 0.0.0.0/0

Phase 2: Certificate Mismatch

Cause:

• ACM missing www SAN

• Wrong cert bound to listener

Fix:

• DNS validation via Cloudflare

• Rebind correct ACM cert

Phase 3: 504 Gateway Timeout

Cause:

• ALB could not reach ECS port 3000

Fix:

• ECS SG inbound TCP 3000 from ALB-SG

Phase 4: 503 Service Unavailable

Cause:

• Target draining during deployment

• No healthy target

Resolution:

• Wait for registration

• Adjust deployment config to prevent downtime

9. Final Cutover Strategy

Grey Release Plan

1. Keep EC2 serving production

2. Deploy ECS services

3. Test via ALB DNS

4. Validate:

   • File access

   • DB consistency

   • Admin CRUD

5. Switch Cloudflare DNS to ALB

6. Monitor

7. Decommission EC2

10. Architectural Evolution

Before:

Single EC2
Filesystem + DB + PHP + Frontend

After:

S3 (storage)
ECS crm-db (database)
ECS crm-backend (API)
ECS crm-web (admin)
ECS gp-web (frontend)
ALB
Cloudflare DNS
ACM TLS

11. DevOps Maturity Achieved

This migration demonstrates capability in:

• Layered infrastructure design

• Zero-downtime deployment logic

• Security Group modeling

• Health check debugging

• TLS and DNS validation

• Stateful → stateless transformation

12. Most Valuable Insight

Error type maps directly to architectural layer:

Understanding this mapping reduced debugging time dramatically.