Modernise Your Legacy Systems Without Disrupting Your Business

Business continuity is built into the architecture of our approach, not bolted on as an afterthought. The Strangler Fig pattern means the legacy system remains the source of truth for each functional area until the replacement has been validated in production. We never decommission any legacy component until its replacement has processed real production traffic successfully over a defined validation period. We also respect your operational calendar — we identify periods where change freeze is appropriate (year-end, peak trading, regulatory deadlines) and plan migrations accordingly. Every stage has a documented, tested rollback procedure.

This is the most common situation we encounter, and it is addressable. Our process for undocumented systems starts with systematic code analysis — reading the codebase to reconstruct business logic, tracing data flows, and identifying the actual rules encoded in conditionals and database procedures. We combine this with intensive workshops with the current users and operators who understand what the system does (if not why). The output of this phase is a business requirements specification that becomes the canonical reference for the replacement, and which also has value as standalone documentation regardless of whether the migration proceeds.

Duration is highly dependent on system complexity, data volume, degree of business criticality and the pace at which your organisation can absorb change. A moderately complex application with a single primary function and a few integrations might be modernised in six to twelve months. A large monolith or mainframe environment that runs core business operations across multiple departments is more typically an eighteen to thirty-six month programme. We phase work to deliver early value — the first migration slices often deliver measurable improvement within the first quarter — so the programme pays for itself progressively rather than requiring full investment before any return.

Yes. We frequently take over modernisation programmes that have stalled, gone over budget or experienced quality issues. Our first step is an honest assessment of what has been built, what is still outstanding and what — if anything — needs to be rebuilt or redesigned. We document our findings without commercial pressure to tell you what you want to hear, and present options for how to proceed. Sometimes the right answer is to continue from where the programme stopped; sometimes significant rework is required. We will tell you which.

Not necessarily. Microservices offer real benefits — independent deployability, technology heterogeneity, team autonomy — but they also introduce significant operational complexity: distributed tracing, network latency, service discovery, and the challenge of maintaining data consistency across service boundaries. For many organisations replacing a legacy system, a well-structured modular monolith is a better starting point: simpler to operate, easier to refactor and deployable as a single unit. We recommend microservices when you have clear functional boundaries that benefit from independent deployment, and teams large enough to own and operate individual services. We are direct about this trade-off rather than defaulting to microservices because they are fashionable.

This is an important question that is often not asked early enough. Our modernisation programmes include structured knowledge transfer to the engineers who will own the replacement system. For organisations whose internal team maintained the legacy system, we work alongside them throughout the programme — they contribute domain knowledge, we contribute modern engineering practices, and the result is a team that is capable of owning the new system rather than dependent on external consultants. The mix of upskilling and knowledge transfer is a core part of our methodology, not an optional extra.