Question 1

What types of legacy systems do you modernise?

Accepted Answer

Our modernisation practice covers a broad spectrum of legacy platforms including IBM mainframe applications written in COBOL, PL/I, and Assembler, as well as Visual Basic 6 desktop applications, classic ASP and COM-based systems, .NET Framework 2.0 through 4.8 applications, and legacy Java EE deployments on JBoss, WebLogic, and WebSphere. We also handle RPG on IBM AS/400 iSeries environments and Oracle Forms applications. Each engagement begins with an automated inventory scan to catalogue every component, dependency, and integration point before any migration work begins.

Question 2

How do you decide between re-engineering, rewriting, or retiring a legacy application?

Accepted Answer

We use a structured assessment framework that scores each application across four dimensions: business criticality, technical debt density, change frequency, and integration complexity. Applications scoring high on business criticality but low on change frequency are typically strong candidates for a lift-and-shift containerisation approach. Those with high change frequency and dense technical debt are evaluated for a strangler fig incremental rewrite. Applications with low business value and duplicated capability elsewhere are flagged for retirement. This evidence-based approach prevents the common failure mode of committing to a full rewrite before understanding the true scope of the system.

Question 3

What is the strangler fig migration pattern and when do you recommend it?

Accepted Answer

The strangler fig pattern involves building new, modern components alongside the legacy system and progressively routing traffic from the old system to the new one until the legacy application can be safely decommissioned. We recommend this approach when the legacy system is actively used in production, when business continuity is non-negotiable, and when the target architecture is significantly different from the source. It is particularly effective for mainframe-to-cloud migrations and monolith-to-microservices decompositions because it eliminates the big-bang release risk. Each slice of functionality is validated independently before the next slice begins, giving stakeholders clear progress visibility and an escape hatch at every stage.

Question 4

How do you handle COBOL mainframe modernisation without disrupting live batch processing?

Accepted Answer

Our mainframe modernisation methodology preserves existing JCL job streams and batch schedules during the transition period through a parallel-run approach where both the legacy mainframe and the modernised platform execute the same workloads and outputs are automatically reconciled. We use automated COBOL-to-Java or COBOL-to-C# transpilation tooling as a starting point, followed by a mandatory human review pass to correct semantic drift and remove dead code paths. Critical batch jobs are migrated one at a time with a defined rollback window. We maintain the mainframe in a read-only shadow state until reconciliation pass rates exceed 99.97% for a minimum of four consecutive business cycles.

Question 5

What automated tooling do you use for legacy code analysis?

Accepted Answer

We deploy a combination of static analysis platforms including SonarQube Enterprise, Understand by Scientific Toolworks, and CAST Highlight to produce dependency graphs, cyclomatic complexity heat maps, and technical debt quantification reports. For mainframe environments, we use Micro Focus Enterprise Analyzer to parse COBOL copybooks and map data flows across programs. For .NET Framework systems, we use the Microsoft .NET Upgrade Assistant combined with custom Roslyn analysers that flag APIs removed in .NET 8. The combined output is aggregated into an executive-level modernisation roadmap with effort estimates, risk scores, and recommended sequencing.

Question 6

How long does a typical legacy modernisation engagement take?

Accepted Answer

Engagement duration varies significantly based on system complexity and the chosen migration strategy. A targeted .NET Framework to .NET 8 upgrade for a mid-sized application typically takes 10 to 16 weeks. A VB6 to modern web stack rewrite for a line-of-business application runs 20 to 36 weeks depending on UI complexity. Full mainframe decommissioning programmes for large enterprises commonly span 18 to 36 months and are structured as a series of quarterly delivery phases. We provide granular timeline estimates only after completing the discovery and assessment phase, as premature estimates made without code-level analysis are a leading cause of modernisation project failures.

Question 7

How do you ensure business continuity during the modernisation programme?

Accepted Answer

Business continuity is treated as a primary constraint rather than an afterthought. We establish a change freeze window with stakeholders for each migrated component, schedule cutovers during low-traffic periods, and maintain fully operational rollback procedures for a minimum of 30 days post-cutover. Integration contracts between the legacy system and downstream consumers are formalised as versioned API specifications before any migration work begins, ensuring that consuming systems continue to function without modification. We also implement feature flag infrastructure so that specific capabilities can be toggled between the old and new implementation paths at runtime if anomalies are detected in production.

Question 8

What cloud targets do you support for modernised applications?

Accepted Answer

Our modernisation practice is cloud-agnostic and supports migration to AWS, Microsoft Azure, and Google Cloud Platform. For containerised workloads, we target Amazon EKS, Azure Kubernetes Service, and Google Kubernetes Engine. For serverless transformation of batch processing, we leverage AWS Lambda, Azure Functions, and Google Cloud Run depending on the client's existing cloud footprint. We also support private cloud targets based on VMware Tanzu and Red Hat OpenShift for organisations with data residency or regulatory constraints that preclude public cloud deployment. Target cloud selection is driven by the client's existing vendor relationships, licensing positions, and operational capability.

Question 9

How do you handle undocumented business logic embedded in legacy code?

Accepted Answer

Undocumented business logic is one of the highest-risk elements of any modernisation programme and we address it through a combination of automated extraction and structured knowledge elicitation. Our code archaeology process uses static analysis to identify decision trees, conditional branches, and calculation routines that lack corresponding specification documents. These are then reviewed with subject matter experts from the client business teams to validate the intended behaviour and create formal acceptance criteria. We build a living business rules catalogue in a version-controlled repository that serves as both the specification for the modernised system and the regression test basis. This catalogue becomes a permanent organisational asset that outlasts the modernisation programme itself.

Question 10

What testing strategy do you use to validate the modernised system against the legacy system?

Accepted Answer

We implement a three-layer validation strategy. At the unit level, we extract test cases from production execution logs and dead code analysis to achieve baseline coverage of all reachable code paths in the legacy system before migration begins. At the integration level, we replay historical transaction logs against both the legacy and modernised systems simultaneously and perform automated output reconciliation to detect semantic differences. At the user acceptance level, we configure shadow traffic routing so that a percentage of live production requests are processed by both systems in parallel with results compared in real time. Discrepancies are categorised as blocking or non-blocking based on business impact and tracked to resolution before any production cutover is authorised.

Question 11

How do you manage database modernisation alongside application modernisation?

Accepted Answer

Legacy applications frequently rely on tightly coupled database structures including stored procedures, triggers, and denormalised schemas that encode business logic in the data layer. Our database modernisation workstream runs concurrently with the application workstream and begins with a schema analysis to classify each stored procedure as pure data access, business logic, or transformation logic. Business logic is extracted into the application tier during the modernisation process. For schema migration, we use AWS Database Migration Service, Azure Database Migration Service, or Flyway depending on the source and target database engines. We also implement bidirectional replication between the legacy and modernised schemas during the parallel-run phase to ensure both systems remain consistent.

Question 12

Can you modernise applications while the client's internal team continues to develop new features?

Accepted Answer

Yes, and we recommend this approach for most enterprise engagements because halting feature development during a multi-year modernisation programme is commercially unacceptable. We establish a branching strategy and integration protocol with the client's internal team at the outset of the programme so that new features developed against the legacy codebase can be cleanly incorporated into the modernised target. For greenfield features developed during the programme, we advise building them directly against the modernised architecture and using the strangler fig pattern to back-integrate them into the legacy system on a temporary basis if needed. This parallel development model requires disciplined API contract management which we establish and govern throughout the engagement.

Question 13

What governance model do you put in place for a multi-year modernisation programme?

Accepted Answer

For programmes spanning more than six months, we establish a dedicated programme management office structure comprising a programme director, technical architect, delivery leads per workstream, and a client-side steering committee. Progress is tracked against a programme roadmap updated fortnightly with completion metrics tied to code migration percentage, test coverage percentage, and outstanding defect counts. We hold monthly steering committee reviews at which we present a red-amber-green status dashboard covering scope, schedule, budget, risk, and quality dimensions. Decision logs, architecture decision records, and risk registers are maintained in a shared programme repository accessible to all stakeholders. We also conduct independent quarterly health checks with a senior architect outside the delivery team to provide objective programme assurance.

Question 14

How do you handle third-party integrations that depend on the legacy system data formats?

Accepted Answer

Legacy systems commonly expose flat-file feeds, proprietary socket protocols, or dated SOAP services consumed by dozens of upstream and downstream systems. We begin by producing a comprehensive integration inventory that maps every inbound and outbound data flow, the consuming system, the data format, and the update frequency. Modern API facades are placed in front of the legacy integration points during the transition period so that consuming systems can be migrated to the new interface on their own schedule rather than requiring a synchronised cutover. For flat-file integrations that cannot be changed due to third-party constraints, we implement adapter components in the modernised architecture that produce the legacy format as an output while the internal data model follows modern standards.

Question 15

What security improvements does modernisation deliver?

Accepted Answer

Legacy systems are disproportionately represented in enterprise vulnerability inventories because they pre-date modern security practices and frequently cannot be patched without disrupting business-critical operations. Modernisation directly addresses this by eliminating end-of-life runtimes and frameworks, replacing proprietary authentication mechanisms with OIDC and OAuth 2.0, and restructuring data access patterns to enforce least-privilege database credentials. We also introduce secrets management using HashiCorp Vault or AWS Secrets Manager to replace hardcoded credentials that are a near-universal finding in legacy codebases. Post-modernisation systems are subjected to a penetration test and SAST scan before production deployment, with findings tracked to closure as part of the programme acceptance criteria.

Question 16

What does the post-modernisation support and knowledge transfer model look like?

Accepted Answer

We include a structured knowledge transfer programme as a formal deliverable in every engagement, not an afterthought. This comprises pair programming sessions between our engineers and the client's internal team throughout the delivery phase, architecture decision records explaining every significant design choice, runbooks for all operational procedures, and a hands-on workshop series covering the modernised technology stack. Post go-live, we offer a 90-day hypercare support period with defined SLA response times during which the client team operates the modernised system with our engineers available for escalation. At the end of hypercare, clients have the option to transition to a retained advisory arrangement for ongoing architectural guidance or to operate fully independently.

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