Search the practice set
126 questions, 454 terms and 400 topics in 20 areas.
42 results for “Migration Risk”
Parallel Run
Running the old and new systems side by side on the same inputs and comparing outputs, before the new one is trusted.
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.
Migration Wave
A batch of applications migrated together, sequenced so that dependencies move in a workable order and each wave delivers learning for the next.
Six Rs of Migration
The standard menu of options for each application in a migration — rehost, replatform, refactor, repurchase, retire, retain.
Slack's Cellular Migration
After repeated availability-zone-level incidents, Slack rebuilt its infrastructure into per-zone cells with the ability to drain traffic away from a failing zone in minutes.
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.
Application Discovery
Establishing what applications exist, what they depend on, who owns them and whether anyone uses them — the step whose absence makes every later step a guess.
Attack Surface
The complete set of points where an untrusted actor can interact with a system — and the quantity that reduction genuinely reduces risk.
CDC Initial Snapshot
The consistent full copy taken when a CDC pipeline starts, before streaming begins — and the step that determines whether the target is correct.
Canary Release
Routing a small fraction of traffic to a new version, watching its metrics, and expanding or rolling back based on what they show.
Capital One's Data Centre Exit
A major US bank closed all eight of its data centres and moved fully to public cloud, treating governance automation as the enabling technology rather than a constraint.
Decision-Making Under Uncertainty
Choosing well when the information is incomplete — by bounding the downside and buying information, rather than by waiting for certainty.
Dual Write
Writing the same change to both the old and new stores during a migration, and the reconciliation that makes it trustworthy.
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.
Reversible Decision
A choice that can be undone cheaply, and which therefore deserves far less deliberation than an irreversible one.
Security vs Usability
A trade-off that is usually resolved by varying the control with the value of the action, rather than by choosing a uniform level of friction.
Step-Up Authentication
Requiring stronger proof of identity at the moment a consequential action is attempted, rather than applying maximum friction to every session.
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.
An estate has database passwords in environment variables across 200 services. Design the migration to a secrets manager.
Sequence it by risk, not by convenience Phase 0 — stop the bleeding. Secret scanning in CI and on the existing repositories, blocking new commits containing cre
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 are asked to lead a migration of 300 applications to cloud. What happens in the first ninety days?
Days 1–30: discovery, and the foundation in parallel Discovery from evidence, not interviews. Network flow logs for dependencies (the only trustworthy source),
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
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
A team wants to move a workload from PostgreSQL to a document store because "the schema keeps changing". What do you ask?
The questions 1. What is actually changing — the shape, or the schema management process? "The schema keeps changing" usually means migrations are painful, not
Security wants mandatory hardware keys for every login; the business says it will cost conversions. How do you resolve it architecturally rather than by picking a side?
What the interviewer is testing Whether you treat security as a fixed dial to be turned up, or as a risk proportionate design variable. Both stated positions ar
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
You must roll out MFA to 40,000 employees. Security wants hardware keys; the service desk fears the call volume. Design the rollout.
The framing that resolves the argument Not every identity carries the same risk, so not every identity needs the same factor. A uniform mandate is what creates
You need to ship a rewrite of the pricing engine. Same inputs, same expected outputs, completely new implementation. How do you release it?
What the interviewer is testing Whether you know that release strategy is part of architecture, and whether you reach for verification techniques beyond "test i
Migration Risk
Bounding blast radius, staging by cohort, and honest readiness reporting.
Cloud Migration
Per-application disposition, sequencing and the capability change underneath.
Data Migration Strategies
Backfill, dual-write, reconciliation and verification.
Database Migration
Moving engines, versions and schemas without losing data or uptime.
Zero-Downtime Migration
Expand, migrate, contract — and the contract phase that never happens.
Change Data Capture
Turning a database's replication log into a stream, and its coupling risk.
Communicating Threat Models
Making risk legible to people who will fund or accept it.
Embeddings
Dense representations, model coupling and the migration they imply.
Mainframe Modernization
Batch windows, COBOL, and the risk profile of core banking systems.
Modernisation Business Case
Pricing tail risk so deferred maintenance becomes fundable.
OWASP Risks
The recurring web and API risk classes, several of which are design flaws.
Presenting to Executives
Decision first, cost, risk, and what happens if we do nothing.