💡 Migrating a Legacy System Handling $1B+ in Transactions — A Multi-Part Journey

A few years ago, we migrated a mission-critical system from PHP Laravel to Node.js — with full data migration, near-zero disruption, and a system that handled over $1B in transactions.

It was one of the most challenging (and rewarding) backend projects I’ve led.

I’ll be breaking this journey down into a few short posts over the next days — each covering a key phase and learning. Here's a quick overview of what to expect:

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⚙️ Part 1: Respect the Legacy Before Replacing It
We didn’t rush into rewriting.
We studied the existing Laravel codebase, identified critical paths, and traced hidden business logic.
Learning: Legacy systems aren’t “bad” — they’re just lived-in. Understand them deeply before you judge.

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🧠 Part 2: Plan the Data Migration Like a Launch Mission
We built detailed scripts, ran mock migrations on staging, and identified edge cases early (timezone issues, orphaned data, etc.).
Downtime: Less than 4 hours.
Learning: Migration isn’t just about moving data. It’s about preserving trust.

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🔀 Part 3: Rebuild With Future Flexibility in Mind
We redesigned using Node.js services — modular, testable, and containerized.
APIs were built with clear boundaries and long-term evolution in mind.
Learning: Don’t just replicate old logic in a new language — rethink the model where needed.

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🧩 Part 4: Align Everyone — Not Just the Tech
We communicated openly with leadership, ops, and clients.
They knew when to expect changes, what the risks were, and how we’d mitigate them.
Learning: A smooth migration is more about people than code.

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✅ Part 5: Rehearse Until It Feels Boring
We did dry runs, rollback tests, shadow traffic, and simulated failovers.
When the real cutover came, it felt like just another rehearsal.
Learning: Boring launches = beautiful launches.

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Over the next few posts, I’ll dive into each phase — what we did, what went wrong, what we learned.

If you've been through a major migration too, I'd love to hear how you approached it.

#BackendDevelopment #NodeJS #SystemMigration #Architecture #Leadership #DataMigration #EngineeringLessons #LaravelToNode #ScalableSystems