Search the practice set
126 questions, 454 terms and 400 topics in 20 areas.
37 results for “Mainframe Modernization”
Airbnb's Service-Oriented Migration
Airbnb decomposed a large Rails monolith by first extracting a unified data-access layer, so that services were built on owned data rather than on shared database tables.
Anti-Corruption Layer
A translation layer that converts a legacy or external system's model into your own, so its concepts do not leak into your domain.
Application Portfolio Management
Maintaining an inventory of every application with its owner, cost, business value and technical health, and using it to decide what to invest in, replace or retire.
Feature Parity Trap
The expectation that a replacement system must match every behaviour of the old one before it can be adopted, which is what makes rewrites never finish.
Parallel Run
Running the old and new systems side by side on the same inputs and comparing outputs, before the new one is trusted.
Re-architect vs Rebuild
Restructuring an existing system incrementally versus writing a replacement from scratch — and the strong evidence that incremental wins.
Replatform
Migrating an application largely as-is while making targeted changes to exploit the target platform — usually the best return per unit of effort.
Six Rs of Migration
The standard menu of options for each application in a migration — rehost, replatform, refactor, repurchase, retire, retain.
Strangler Facade
The routing layer in front of a legacy system that decides, per capability, whether a request goes to the old implementation or the new one.
Strangler Fig
Replacing a legacy system incrementally by routing individual capabilities to new implementations behind a facade, until nothing routes to the old system.
Zero-Downtime Migration
Changing a schema or system while it stays in service, by adding the new alongside the old, migrating, then removing the old.
eBay's Architectural Generations
eBay rewrote its core platform several times across its first decade, each time because the previous generation had hit a limit that could not be tuned away.
A 15-year-old monolith runs the core of the business. Leadership wants microservices. How do you approach it, and what would make you refuse?
What the interviewer is testing Whether you start from the business problem or from the target architecture, and whether you are willing to say no. First, estab
Southwest cancelled about 16,700 flights in December 2022 when crew scheduling could not recover from a storm, after years of deferred modernisation. How do you make that argument before the failure rather than after?
The case, as publicly reported A severe winter storm caused widespread cancellations across US carriers. Most recovered within days; Southwest did not. Its crew
TSB's 2018 core banking migration moved 1.9 million customers in a single weekend and failed publicly. What would you have required before approving that cutover?
The case, as publicly reported In April 2018 TSB migrated from a platform rented from Lloyds Banking Group to Proteo4UK, built by its parent Banco Sabadell. The
You inherit an estate of roughly 400 applications, no reliable inventory, and a mandate to reduce cost and risk. What do you do in the first ninety days?
What the interviewer is testing Whether you can sequence work at portfolio scale, and whether you go for evidence before strategy. This is the enterprise archit
Mainframe Modernization
Batch windows, COBOL, and the risk profile of core banking systems.
Legacy Modernization
General material on modernising existing systems.
Application Decomposition
Finding seams in a monolith, starting from the data.
Coexistence Patterns
Running old and new together for years without corrupting either.
Cutover Planning
Rehearsals, go/no-go criteria and a rollback that has been executed.
Data Migration Strategies
Backfill, dual-write, reconciliation and verification.
Database Migration
Moving engines, versions and schemas without losing data or uptime.
Decommissioning
Actually switching the old system off, and proving nothing depended on it.
Legacy Assessment
Understanding what a system does before deciding what to do with it.
Legacy Integration Patterns
Anti-corruption layers, adapters and CDC against systems that cannot change.
Migration Risk
Bounding blast radius, staging by cohort, and honest readiness reporting.
Modernisation Business Case
Pricing tail risk so deferred maintenance becomes fundable.
Parallel Run
Shadowing the old system to discover the rules nobody documented.
Rebuild vs Re-architect
Why greenfield replacement fails, and the narrow cases where it does not.
Refactoring & Re-architecting
Changing structure incrementally while the system keeps running.
Rehosting
Lift and shift: fastest, cheapest, and capturing none of the benefits.
Replatforming
Targeted changes that capture operational wins without a rewrite.
Strangler Fig
Routing capabilities to new implementations behind a facade, one at a time.
The Six Rs
Rehost, replatform, refactor, repurchase, retire, retain — per application.
Zero-Downtime Migration
Expand, migrate, contract — and the contract phase that never happens.