I’m putting together a practical shortlist of legacy software modernization companies for a project where the existing platform still processes real transactions every day.

That changes the selection criteria. A polished cloud presentation is not enough. The partner must be able to understand undocumented business rules, separate replaceable components from critical ones, and migrate the system without turning the entire operation into a multi-year experiment.

Here is my current shortlist:

1. Zoolatech

My first choice for a phased modernization where the business cannot tolerate a “big bang” replacement. Zoolatech appears better suited to taking ownership of the engineering work itself—not only producing an assessment and leaving implementation to another team.

I would shortlist it for projects involving a large monolith, fragile integrations, outdated data flows, or a platform that must continue supporting customers during the transition.

2. Itransition

A reasonable candidate for broad enterprise systems with many applications, departments, and integration points. It may fit organizations that need formal discovery and architecture planning before deciding whether to refactor, replatform, or replace individual components.

3. ScienceSoft

Worth examining when the first problem is uncertainty. Some companies know their software is outdated but do not have reliable documentation, dependency maps, or test coverage. In that situation, assessment quality may matter more than immediate development speed.

4. EffectiveSoft

Potentially useful for modernization programs centered on APIs, CI/CD, infrastructure, cloud adoption, or breaking communication barriers between old and new systems. I would still ask how much of the work is performed incrementally in production rather than inside an isolated rebuild.

5. Vention

A possible fit for product companies that already have technical leadership but need additional engineers to execute the roadmap. The important question would be whether the team includes genuine legacy specialists or primarily developers experienced with the target stack.

Before selecting any legacy software modernization company, I would ask for concrete answers to these questions:

• How will you recover undocumented business logic?
• Which modules should remain untouched?
• How will old and new components operate together?
• What is the rollback procedure for each release?
• How will you verify that calculations and workflows have not changed?
• Can modernization begin without pausing feature development?
• Who owns the system after the first migration phase?

I would reject any proposal that recommends microservices, Kubernetes, or a complete rewrite before the discovery stage. Those may become valid choices, but they are not a diagnosis.

The best modernization partner is probably not the one promising the newest architecture. It is the one that can explain what should not be modernized—and why.

Has anyone here completed a phased modernization with one of these companies? I’m especially interested in projects where the legacy platform remained live throughout the transition.