The "Big Bang" Migration

The Challenge: A 500k User Bottleneck

A fast-growing EdTech company reached a critical tipping point. With 500,000 active users and a contract signed to onboard another 200,000 users immediately, the legacy infrastructure hit a wall.

The platform was built on a rigid WordPress/PHP monolith.

• The Logic Trap: A single error in the payment gateway could crash the student login portal.
• The Data Straitjacket: The database used a hardcoded "School -> Class" hierarchy. New B2B customers requested "District" and "Regional" management layers, but the schema couldn't support it without a total rewrite.
• The Deadline: With the new customers waiting, we didn't have time for a gradual "Strangler Fig" migration. We had to execute a complete platform overhaul before the school year started.

The Solution: Strategic Decoupling

Acting as the Technical Lead, we executed a high-stakes "Big Bang" migration, rewriting the core platform into a Node.js Microservices ecosystem.

1. The "Dynamic Levels" Data Innovation

The most critical bottleneck wasn't code; it was the data model.

• Old Way: Hardcoded tables for Schools and Classes.
• New Way: We implemented a Recursive Dynamic Hierarchy. This allowed the business to create infinite organizational layers (e.g., State -> District -> Region -> School -> Class -> Group) instantly, without touching the code.
• Impact: This single change future-proofed the business model for complex B2B sales.

2. Microservices Architecture (Node.js)

We broke the monolith into 10 autonomous services (Auth, Content, User Mgmt), each communicating via REST APIs.

• Isolation: Each service owned its own MySQL database. This ensured that a complex report query didn't lock the table for students trying to log in.
• Future-Proofing: While deployed initially in one region, the codebase was architected with Region-Aware Routing logic from day one, ready to scale globally to the AWS region closest to the user.

3. Pragmatic Frontend Strategy

With budget constraints tight, we made a strategic decision:

• Legacy: We stabilized and kept the existing AngularJS frontend for the core product to save costs.
• Modernization: For all new applications and logic decoupled from the monolith, we utilized Vue.js, creating a hybrid ecosystem that allowed for innovation without breaking the bank.