Fixing legacy bugs — the main blockers for further product support and development

Case Study

Onpex provides multi-currency IBAN accounts, transaction banking and FX services. Onpex operates API-driven BaaS platform that allows clients to create user-friendly, compliant and cost-efficient payment and banking solution.


ONPEX is a leading provider of transaction banking and cross-border payment services to fintech and digital businesses. ONPEX provides simple and automated access to multi-currency IBAN accounts, transaction banking, and FX services. Their flexible, API-driven BaaS platform allows clients to create user-friendly, compliant and cost-efficient solutions.

Project Overview

ONPEX had a legacy system in place that was hindering their growth and was not allowing them to reach their business objectives. Furthermore, there were all kinds of bugs inside the system that needed to be removed so the system could function properly. Team Harbour was tasked with providing change management services and fixing all of the bugs.

Business Issue

The legacy system that was in place was not allowing ONPEX from maintaining usual business activities for many reasons. First of all, it had a lot of components that did not completely match each other or greatly slowed down work, or did not work at all. This was making things very difficult for ONPEX’s employees. What made matters worse was that the internal IT staff was let go since they were not able to maintain the system. ONPEX approached Team Harbour with the challenge of providing the needed system maintenance and bug fixes.

Technological Solution

We had two months to take more than 500,000 lines of code that was written by ONPEX’s internal teams and analyze it to identify the bugs that needed to be fixed. We also needed to change the payment connections as well. We created an onboarding plan that included:

Creating a new CI/CD environments with the actual production version Review the existing versioning policy, moving to standard and robust “Git flow” Reverse-engineering for revealing a specific and important functionality Reconstruction of the whole architecture scheme and thoroughly documenting it Making the first “no-features” release deployment to check the release deployment process Lastly, go to bug-fix and feature releasing

We assembled a team of eight people consisting of a PM, Tech Lead, 2 senior Java developers, BA, QA and DevOps. Since we understood the importance of DevOps in this project, we hired a Lead DevOps engineer on a full-time basis to complement the one we had on staff.

We only had two months to make all of the hotfixes, create the new connectors and redeploy everything with new infrastructure. Then the next phase of the project would begin which included 12 months for further support and development.


ONPEX received a revamped system that was free of any bugs and with new payment connectors. During the first two months, the huge system, which contained more than 500,000 lines of code was redeployed on the new infrastructure. All of the main old bugs were fixed and necessary connection activities were done. Everything was done on time with a team that was two times smaller than the one they had before and with very limited business and technical descriptions of the system.


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