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The riskiest legacy migration is the one that runs in a single cutover weekend. We run the kind that takes eighteen months and produces zero customer incidents.
Incrementally transform core systems without stopping the business that runs on them.
BNS decomposes legacy platforms using strangler-fig patterns, event-driven migration, and parity-tested cutovers — with zero tolerance for customer-visible downtime.
BNS modernises the platforms that enterprises can't stop — core systems, claims engines, booking stacks, billing platforms. The riskiest program is the big-bang rewrite. We decompose legacy monoliths behind typed contracts, extract domains onto event-driven foundations, and run parallel validation against the production system until the cutover risk is gone. Every program ships features to real users throughout the migration — the business doesn't pause for the platform to catch up.
Our principal engineers have led migrations at comparable scale and carry the scars. Kill-switch criteria, parity thresholds, and rollback gates are negotiated before a single line is merged. Biweekly production drops keep stakeholders honest and leadership informed — with cloud and platform foundations designed for the target architecture from the first sprint, not retro-fitted at the end.
Domain mapping, dependency analysis, and a sequenced migration plan with kill-switch criteria.
Domain-by-domain extraction behind typed contracts, with parity tests run against production continuously.
Parallel-run window: shadow traffic, divergence monitoring, and stakeholder sign-off against agreed thresholds.
Rehearsed production cutover with feature flags, automated rollback gates, and live war-room coverage.
Incremental extraction behind typed contracts, with feature parity proven in production before cutover.
Domain migration onto event-sourced, CQRS-ready foundations with replay and audit built in.
Schema evolution, dual-write windows, and reconciliation engines that keep source and target in sync.
Shadow traffic, parity testing, and automated divergence alerting across migration windows.
Zero-downtime cutovers with rehearsed rollback criteria, feature flags, and war-room runbooks.
Legacy point-to-point replaced with contract-tested, versioned APIs and event meshes.
BNS is technology-neutral by policy — our engineers work across the open-source and commercial stacks that enterprise platforms actually run on.
Every BNS-led cutover is rehearsed in a production-equivalent environment with automated rollback gates. Kill-switch criteria are agreed in advance — if parity thresholds are not met, the cutover does not proceed. Clients cut over without a customer-visible incident because the discipline starts in sprint one, not cutover weekend.
Strangler-fig extraction is sequenced so product teams keep shipping to real users throughout the programme. No freeze, no feature moratorium. Business velocity is a success criterion, not a sacrifice — and release frequency on the target platform is measured from the first extraction sprint.
Each extracted domain reduces the coupling tax on the remaining legacy system. Cost-to-change on the target platform runs 58% lower than the legacy baseline within the first year of live operation — because typed contracts, event sourcing and documented seams replace implicit dependencies and tribal knowledge.
Runbooks, architecture-as-code, domain ownership maps and on-call playbooks are handed back at the end of every migration. The platform is documented and transferable — no dependency on BNS to understand the seams or run the next migration increment.
Parity test suites, divergence dashboards, and rollback rehearsals give the program team a live risk register through the migration window — not a RAG status updated once a fortnight. Leadership sees what the engineering team sees, on the same cadence.
Our principal migration engineers have led tier-1 core system replacements inside banks, insurers, telcos and utilities. They have rehearsed the rollback that never fires and the one that did — and the programme plans they write reflect both.
BNS is technology-neutral — we migrate to the architecture the domain calls for, not the one we happen to have trained most recently. The migration plan follows the risk and operating model, not a vendor roadmap.
United States delivery operations mean cutover weekends have senior engineers in every region. The war room does not go dark at 6pm local — it runs until the migration is confirmed stable.
ISO 27001, SOC 2 Type II and regulatory posture are maintained across the migration window — no temporary exception for the cutover environment. Audit trails, access controls and SBOM artefacts cover the migration tooling as well as the production systems.
Measurable outcomes from the platforms our engineers shipped this year.
Rebuilding the core while the business still runs on it is harder than greenfield, and more valuable than anything else you will ship.
Why fixed-price is rarely the right answer, outcome-based contracts are harder than you think, and the model that wins is neither.
Boards over-index on burn-rate and under-index on delivery signal. The five charts that change the room.
We prefer incremental extraction over rewrites — the evidence is clear on which produces fewer incidents.
Yes. We run a two-week stabilisation audit and take over from whatever state the program is in.
Custom business applications engineered for the load, risk and scale of your organisation.
Landing zones, platform teams and SRE practices that make cloud a business advantage.
Implementation, extension and integration of the systems that run operations.
Share your brief and we’ll assemble two senior legacy modernisation practitioners for a 90-minute working session — no deck, no sales.