We’ve all been there. You open a repository, see NestJS 7 and AWS SDK v2, and your heart sinks. You start mentally preparing for weeks of "dependency hell," breaking changes, and the inevitable "why is this type not assignable to itself?" debugging sessions.

I recently faced a migration mountain that I thought would be a total nightmare:

AWS SDK v2 → v3 (The massive shift to modular packages).

NestJS 7 → NestJS 11 (Bridging a four-major-version gap).

TypeORM + Peer Deps (The classic domino effect of updates).

Deployment Overhauls (Compatibility fixes and CI/CD tweaks).

I expected weeks of pain. It took 48 hours.

The secret wasn't just "using AI"—it was using Codex with ChatGPT 5.1 as a legitimate engineering partner.

AI Didn’t Replace My Experience; It Amplified It

The biggest takeaway from these two days was a shift in my role. I wasn't just a "coder" anymore; I was a high-level architect overseeing a very fast, very efficient assistant.

By offloading the repetitive, error-prone parts of the migration, I could stay in a state of "focused execution."

How the Workflow Looked:
Refactoring Legacy Code: Instead of manually rewriting every AWS service call to the new Command pattern in v3, I used the AI to transform blocks of code while I verified the logic.

Bridging the Version Gap: NestJS has changed a lot since version 7. ChatGPT 5.1 helped identify deprecated decorators and injection patterns instantly, saving me hours of digging through old documentation.

Fixing TypeORM "Gotchas": We all know how finicky TypeORM can be during upgrades. The AI was a lifesaver for identifying schema mismatches and fixing subtle breaking changes in the QueryBuilder.

Deployment Checks: It helped me write and verify the compatibility fixes needed for the new environment, ensuring that once the code was done, it actually ran.

From Migration to Creation: The MTKits Story

To prove this wasn't a fluke, I used the same "AI-amplified" workflow to build MTKits.

MTKits is a collection of developer utilities (like JSON formatters and JWT tools) that I’ve always wanted to exist in one clean place. By letting the AI handle the "boilerplate" utility logic, I was able to build and launch the entire site in just a few days.

The Reality Check
If you’re still just watching AI demos or using it to write "Hello World" apps, you’re missing the real value. The true power of tools like Codex and ChatGPT 5.1 shines when you throw them at messy, real-world production tasks.

It doesn't replace the need for a senior dev’s intuition—you still need to know what to build and how to verify it—but it removes the "friction" of getting there.

My advice? Pick that one migration task you've been dreading for months. Open up your AI assistant of choice, and see how much faster you can move when you're thinking at a higher level.

Have you tried a major refactor with AI yet? I’d love to hear if your experience was as smooth as mine was! 👇