--- title: "Application modernization" description: "Assessment, incremental migrations, re-platforming, database modernization and cloud native refactoring, in steps that each deliver value." url: https://www.expandware.com/services/engineering/application-modernization/ section: "Services" topics: ["Engineering", "Strangler fig pattern", "Domain-driven design", "Containers", "Kubernetes"] publisher: "Expandware Private Limited" --- # Application modernization Assessment, incremental migrations, re-platforming, database modernization and cloud native refactoring, in steps that each deliver value. Modernize the legacy system without stopping the business. Legacy systems are usually legacy because they work and the business depends on them, and rewriting them in one project is the riskiest way to replace them. We modernize in increments: put a stable interface in front of the old system, move capabilities one at a time to new services behind it, migrate data alongside, and retire the old parts as they empty. Each step delivers something useful and can be reversed. Where it usually starts: - A core system runs on a platform or language few people still support. - Every change to the old system takes weeks and carries risk. - A rewrite was attempted once and abandoned. - The system cannot move to the cloud as it is. What is included: - Portfolio assessment: Each application assessed to retain, rehost, replatform, refactor, replace or retire. - Incremental migration: New services built around the old system, with traffic moved over gradually. - Re-platforming: Applications moved to supported runtimes, containers or managed services. - Database modernization: Data moved off legacy databases with validation and reconciliation. - Coexistence: Interfaces that let old and new systems run side by side during the transition. - Retirement: Old components decommissioned once their last user has moved. Where it sits: Modernization works on the production side of the engineering architecture: it puts a stable interface in front of the legacy system and moves capabilities to new production services one at a time. Decisions to settle early: - Modernize or replace. A commodity capability is often better replaced by a product; a differentiating one is worth modernizing. The call is made per capability. - Which capability first. Starting with something valuable and separable proves the approach. The seams in the system decide. - How long old and new coexist. Coexistence costs money but removes risk. The roadmap sets an end date for each part of the old system. How the work runs: Assess, Code, data and dependencies. Wrap, A stable interface in front. Replace, Capabilities moved one at a time. Retire, Old parts decommissioned. How it is bought: - A fixed-fee assessment: We read the code, data and interfaces of the system and find the seams where it can be divided. You receive the assessment, a roadmap outline and a fixed price for the first increments. - A fixed-price build: Each increment, wrapping, replacing a capability, migrating its data and retiring the old part, is priced before it starts. - Running it afterwards: Between increments, the coexisting systems can be operated by your team or by us, and the roadmap is reviewed as each step lands. Worked example, a core system nobody wants to touch. Say an insurer's policy administration system runs on an old platform that few engineers still know. Every change takes weeks, a full rewrite was abandoned once, and its hosting cannot follow the rest of the estate into the cloud. - Assess: We read the code, data and interfaces, map which capabilities matter most, and find the seams along which the system can be divided. - Wrap: A stable API is placed in front of the old system, so other applications stop depending on its internals. - Replace: Quoting moves first to a new service behind the API, with traffic shifted gradually and the old path kept as a fallback. - Retire: As each capability moves and its data is reconciled, the matching part of the old system is switched off. At the end, each step has delivered something the business uses, the old system shrinks with every release, and no single cutover has put the business at risk. (An illustration, not a client account.) What you have at the end: - Application assessment and modernization roadmap: The condition of each application and the path chosen for it, in a sequenced plan. - Target architecture: The design the system is moving towards, and how old and new parts coexist on the way. - Incremental migration plan: The order in which capabilities leave the old system, each step usable and reversible. - Data migration and reconciliation reports: Each data move validated against the source, with discrepancies resolved and recorded. - Decommissioning records: Evidence that each retired component was switched off, archived and removed safely. Standards and platforms worked with: Strangler fig pattern, Domain-driven design, Containers, Kubernetes, PostgreSQL, .NET, Java, Event streaming. Where it goes wrong, and what we design out: - The big rewrite. Replacing a core system in one project is the riskiest way to do it. Capabilities move one at a time. - Changing behavior by accident. Without tests, nobody knows what the old system really does. Characterization tests record it first. - Data left for last. Moving code without its data leaves both systems half alive. Data moves with each capability. What it changes: - Value at every step. Each increment delivers a working improvement, not a promise at the end. - Risk kept small. Changes are small and reversible, so a failure is a rollback rather than a crisis. - A platform people can change. Modern services can be changed quickly by engineers you are able to hire. How you will know it is working: - Every increment delivers something the business uses. - The legacy system shrinks with each release. - Each step can be reversed. - Changes take days instead of weeks as more capability moves. Who you work with: - Modernization architect. Assesses the system, finds its seams and designs the target architecture. - Software engineers. Build new services, characterization tests and the coexistence layer. - Data engineer. Migrates and reconciles data as each capability moves. What we need from you: - Access to the source code, databases and environments. - People who know how the system is used, and its quirks. - Business owners for each capability. - Tolerance for change windows during migration. Common questions: Q: Why not rewrite the system from scratch? A: Because a big rewrite has to match years of behavior before it delivers anything, and many fail before they do. Incremental modernization delivers value early and keeps the option to stop at any point. Q: How do you understand an undocumented legacy system? A: By reading the code, tracing the data and watching the system in production, and by talking to the people who use it. The findings become the documentation the system never had. Q: Can the old and new systems run side by side? A: Yes, that is the point of the approach. An interface routes each request to whichever system currently owns that capability, and data is synchronized until the old system is retired. Q: How is a modernization program priced? A: One increment at a time. The first is chosen to be small enough to reach production quickly, and each one after it is planned and priced on its own, so you can stop when the value runs out. Q: What is the strangler fig pattern? A: A way of replacing a system gradually: new services are built around the old one behind a common interface and take over its capabilities one at a time, until the old system can be switched off. It is named after a plant that grows around a tree and eventually replaces it. Q: Should we replace a legacy system with a packaged product instead? A: Sometimes. If the system does what many products already do, such as accounting or HR, a package is often the better answer. If it embodies how your business competes, modernizing it usually keeps more value. The assessment makes that call for each capability, not for the system as a whole. Q: How do you modernize a system that has no tests? A: By writing characterization tests first, which record how the system behaves today, quirks included, before anything is changed. They become the safety net that shows whether a new service behaves the same as the part it replaces. Q: What happens to the data in the old system? A: It moves with the capabilities that own it, and is validated and reconciled against the source at each step. History that no longer needs to be live can be archived in a form that stays queryable for audit and legal purposes. Often paired with: Software and product engineering, Cloud strategy and migration, Application and API integration. --- Canonical page: https://www.expandware.com/services/engineering/application-modernization/ Site index for machines: https://www.expandware.com/llms.txt Full site text: https://www.expandware.com/llms-full.txt Expandware Private Limited. Inquiries: solutions@expandware.com, +92 (333) 32 11011.