# Does Migrate a Monolithic System to Microservices Decrease the Technical Debt?

## TL;DR

This case study investigates how migrating from a monolithic system to microservices impacts technical debt, showing an initial increase but long-term reduction in debt growth.

## Contribution

It provides empirical evidence that microservices migration can reduce technical debt growth over time, based on a four-year case study.

## Key findings

- Initial spike in technical debt during migration
- Long-term slowdown in technical debt growth
- Microservices help reduce technical debt in the long run

## Abstract

Background. The migration from monolithic systems to microservices involves deep refactoring of the systems. Therefore, the migration usually has a big economic impact and companies tend to postpone several activities during this process, mainly to speed-up the migration itself, but also because of the need to release new features. Objective. We monitored the Technical Debt of a small and medium enterprise while migrating a legacy monolithic system to an ecosystem of microservices to analyze changes in the code technical debt before and after the migration to microservices. Method. We conducted a case study analyzing more than four years of the history of a big project (280K Lines of Code) where two teams extracted five business processes from the monolithic system as microservices, by first analyzing the Technical Debt with SonarQube and then performing a qualitative study with the developers to understand the perceived quality of the system and the motivation for eventually postponed activities. Result. The development of microservices helps to reduce the Technical Debt in the long run. Despite an initial spike in the Technical Debt, due to the development of the new microservice, after a relatively short period, the Technical Debt tends to grow slower than in the monolithic system.