Legacy software modernization without a full rewrite: one workflow at a time, with the system still running

Hashlogics modernizes legacy software without a full rewrite: we wrap the old system in an API, move one workflow at a time onto new code, keep both running until the new path proves itself, and retire the old part only when nothing depends on it. Senior engineers do the work and maintain the result.

They include reading what the old system really does, choosing the first workflow to move, building the new path beside the old one, migrating and reconciling the data, switching traffic gradually with a way back, and retiring the old code. Maintenance after launch should be part of the same contract.

Ask how they will learn what the old system does, which workflow moves first, how old and new run side by side, what the way back is, and who maintains the result. A firm that answers with a weekend cutover plan is selling a rewrite.

When the old system can't be reached through any interface, when its platform no longer gets security fixes and can't be isolated, or when it is small enough to rebuild in one milestone. Otherwise modernizing in slices pays you sooner and carries less risk.

Yes, that is the point of the approach. New paths run beside the old ones and take traffic gradually, so there is never a moment where everything depends on one cutover. Cruise Search AI went into a live WordPress site that stayed up throughout.

One slice at a time, with one decision per slice: rehost, refactor or rebuild. Each slice moves with its data, runs beside the old version, and switches over only after it carries real load, so the cloud move never depends on a single cutover.

That is the normal case. We start with a free scoping call to see what you have and what you need. Every build starts with a fixed-fee Blueprint: an engineer reads your real systems and writes the plan, with a fixed price for each milestone rather than a guess. The fee is credited in full against the build, and if the plan isn't one you'd act on, you don't pay for it. We read the code and watch what the system actually does in production. Behaviour and documentation always disagree by the time a system is old. You get a written map of what is there before anyone proposes changing it.

One system owns each record at any moment, and which one is written down before anything moves. While both run, a daily reconciliation compares them so a mismatch is found by us rather than by your finance team. Repeated requests are built to be harmless, because timeouts make the same call arrive twice.

Rarely on its own. Old versions matter when they stop receiving security fixes or block an integration you need, and then upgrading is unavoidable. Being old is not the same as being wrong, and replacing working code because it is unfashionable spends budget without buying anything.

You can usually add it without replacing anything, because AI reaches the old system through its existing interfaces. Cruise Search AI is an AI module inside a WordPress site, backed by FastAPI and LangGraph, handing validated searches to the client's own engine. The old system stayed exactly as it was.

Take the workflow with the highest pain and the cleanest edges. Pain gives you a benefit people notice; clean edges mean it can move without dragging half the system with it. Where those two point at different workflows, we start with the one that can be reversed most easily.

Cost is driven by how tangled the old system is, how many integrations depend on it, and how much of its behaviour is undocumented. Nobody can quote that responsibly from the outside, which is why every build starts with a fixed-fee Blueprint, credited in full against the build. You get a fixed price for the first slice, then decide whether to continue. The first 2 months of support and maintenance are free, with every build.