Legacy Application Modernization Services

Most legacy systems are not broken. They are expensive to change, hard to hire for, and stuck on frameworks that no longer receive security patches. A full rewrite sounds like the clean answer, but big-bang rewrites routinely overrun, ship late, and lose business logic that lived only in the old code. We take a different route.

We modernize incrementally. New, well-tested services grow alongside the running monolith and gradually take over its responsibilities until the old code can be retired safely. You get continuous business value, lower risk, and a production system that never goes dark during the transition. Every engagement is led by our founder Gopal Sabhadiya (Toptal top-3%, Expert-Vetted on Upwork, ex-Infosys Specialist Programmer), backed by a focused team of 10.

Incremental modernization with the strangler fig pattern

The strangler fig pattern lets us modernize a live system without stopping it. We place a facade or API gateway in front of the existing application and route incoming requests through it. At first, every request still goes to the old monolith. As we build each replacement capability as a new Spring Boot service, we update the routing so that the new code handles that slice of traffic, while everything else continues to flow to the legacy system.

This reverse-proxy-driven incremental cutover means each step is small, observable, and reversible. If a newly extracted service misbehaves, we route that path back to the monolith in seconds. Over time the new services take over more and more, and the original codebase shrinks until it can be decommissioned. This is how we avoid the budget overruns and lost business logic that sink big-bang rewrites, and how we keep your team shipping features during the migration instead of freezing development for a year.

From Java EE to Spring Boot and Jakarta EE

The most common modernization we run is Java EE to Spring Boot. We lift applications off legacy application servers such as WebLogic and WebSphere onto self-contained Spring Boot deployments. EJBs are refactored into Spring beans with declarative transactions and Spring AOP for cross-cutting concerns; JNDI-bound datasources move to externalized configuration through environment variables, ConfigMaps, and Secrets; and the persistence layer is modernized on Hibernate and JPA.

The javax-to-jakarta namespace change is a hard requirement for anything moving to Spring Framework 6 and Spring Boot 3, which target Jakarta EE 10. We treat this as automated code transformation rather than manual editing, using OpenRewrite recipes, Eclipse Transformer for bytecode-level migration, the Apache Tomcat Jakarta migration tool, and the Spring Boot Migrator where it fits. For teams on Spring Boot 2, we run the Spring Boot 2 to 3 migration as a planned sequence: dependency upgrades, the jakarta namespace switch, configuration property changes, and then verification against your existing test suite. Every transformation is committed in small, reviewable steps.

Breaking the monolith into microservices

We do not split a monolith for its own sake. We decompose it along bounded contexts, the natural seams in your domain where data and behavior genuinely belong together. Authentication, billing, catalog, and reporting are typical first candidates because they have clear boundaries and clear ownership.

Our USP.org engagement shows this in practice: we extracted authentication into a dedicated Spring Boot and Spring Security microservice that is horizontally scalable and serves more than 500,000 users. Each extracted service is containerized and runs on Kubernetes, with independent scaling and deployment. The result is reduced technical debt, faster release cycles, and an architecture your team can reason about service by service instead of wrestling with one large, fragile codebase.

Refactor, rewrite, or replatform: choosing the right path

Not every system needs the same treatment, so we start with an assessment against the 6 Rs framework: rehost, replatform, refactor, rearchitect, and retire. Some components are best lifted onto a modern runtime with minimal change; others justify deeper refactoring or rearchitecting into services; a few are candidates for retirement once their functionality moves elsewhere.

We deliver an enterprise application modernization roadmap that sequences this work to maximize business continuity and minimize risk. The default answer to refactor versus rewrite is almost always incremental refactoring, because it preserves hard-won business logic and keeps the system earning revenue throughout. We recommend a rewrite only where the existing code is genuinely beyond salvage, and even then we phase it behind the same strangler fig facade.