About
We helped a regulated crypto trading platform modernise its backend by incrementally rewriting a poorly structured Express system into a stable NestJS architecture. Our team improved code quality, strengthened AML compliance, managed AWS EC2 deployments and delivered new backend features without disrupting live trading.
Challenge, approach, and impact
Outdated and fragile backend
The platform relied on a large legacy repository written in Express that had grown chaotic over the years. Its inconsistent structure, duplicated logic and weak separation of concerns made even small changes risky. This technical debt slowed delivery, reduced reliability and prevented the platform from scaling with rising user and transaction volumes.
Rising compliance demands
As a regulated crypto exchange, the client needed a modern AML solution with accurate, real-time access to user and transaction data. The old backend could not reliably support these integrations, exposing the business to operational and regulatory risks. Strengthening compliance became essential for protecting the platform and maintaining market trust.
A live, high-volume environment
The migration had to be carried out without disrupting deposits, withdrawals or trading activity. Any downtime could affect thousands of users and damage trust. This required a careful, incremental approach that allowed new components to be introduced gradually while keeping core financial workflows stable and responsive.
Limited ability to scale
The monolithic architecture struggled during peak trading periods and could not scale efficiently. Adding new functionality or optimising existing features often introduced regressions. The platform needed a modern foundation capable of supporting growth, faster development and more predictable performance under load.
Feature development during migration
The client still needed to roll out new product capabilities, including a Dust Converter for optimising small crypto balances. These features had to be developed on top of a legacy codebase that was already under migration, requiring careful coordination and robust engineering practices to avoid instability.
How we built
Testimonials
Michał Skorzec, Backend Developer @ DO OK
DO OK
“orking on this project was both challenging and rewarding. We were modernising the heart of a busy crypto platform while it stayed live, which demanded focus and teamwork. Seeing the system become more stable, more secure and easier to build on was incredibly satisfying. It was a demanding project, but also one of the most interesting I have been part of.“
Team structure
Client team
Adam
Technical Manager
Daily point of contact
The client stakeholders were working closely with the team at DO OK
Agency team
2 x Backend Developer
Production