Search the practice set
126 questions, 454 terms and 400 topics in 20 areas.
31 results for “Zero-Downtime Migration”
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.
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.
Secret Zero
The credential a workload needs in order to authenticate to the secret manager — the one secret that cannot itself be stored in the secret manager.
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 Trust
A security model that grants no implicit trust from network position, and authenticates and authorises every request individually.
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.
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.
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.
Dual Write
Writing the same change to both the old and new stores during a migration, and the reconciliation that makes it trustworthy.
Figma's Postgres Sharding
Figma delayed sharding for years using replicas and vertical partitioning, then sharded Postgres horizontally without downtime using logical shards and a proxy layer.
Microsegmentation
Enforcing fine-grained network policy between individual workloads rather than between broad network zones, so a compromise cannot move laterally.
Parallel Run
Running the old and new systems side by side on the same inputs and comparing outputs, before the new one is trusted.
Replatform
Migrating an application largely as-is while making targeted changes to exploit the target platform — usually the best return per unit of effort.
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.
A board mandate says "implement zero trust in twelve months". What do you actually do, in what order?
First, reframe the mandate Zero trust is not a project with an end date; it is a posture reached incrementally. A twelve month programme promising completion wi
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),
Your services currently trust anything inside the VPC. A security review says move to zero trust. What changes, and what will it cost you?
What the interviewer is testing Whether "zero trust" is a concrete set of changes to you, or a slogan. What actually changes Workload identity. Every service ge
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
Zero-Downtime Migration
Expand, migrate, contract — and the contract phase that never happens.
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.
Migration Risk
Bounding blast radius, staging by cohort, and honest readiness reporting.
Zero Trust
No implicit trust from network position; authorise every request.
Embeddings
Dense representations, model coupling and the migration they imply.
Serverless
Scale to zero, per-request billing, cold starts and connection limits.