Search the practice set
275 questions, 991 terms and 600 topics in 30 areas.
60 results for “Warehouse Migration”
Report Migration Inventory
The enumerated list of every report, extract and downstream consumer of the legacy warehouse, with usage evidence, which is what makes the migration finite.
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.
Database Migration Strategy
The approach for moving data to a new store, which is usually the longest pole and the highest risk in any modernisation.
Embedding Model Migration
The process of moving a corpus to a new embedding model, which requires re-embedding everything because vectors from different models are not comparable.
Expand-Contract Migration
Changing a schema in additive steps that keep old and new code both working, so deployment and migration never have to be simultaneous.
Migration Risk Register
A maintained record of what could go wrong in a migration, with likelihood, impact, owner and mitigation, reviewed as the programme progresses.
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.
Warehouse Concurrency Scaling
Adding compute clusters to absorb concurrent queries rather than queueing them, and the cost behaviour that turns a queue into a bill.
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.
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.
Coexistence Period
The interval during which old and new systems both operate, which is longer, more expensive and more complex than migration plans usually assume.
Cutover Runbook
The step-by-step plan for a migration event, including verification points, decision criteria and the rollback path, rehearsed before it is used.
Data Lakehouse
A pattern that puts warehouse-style transactions, schema and governance on top of cheap open-format object storage.
Decommissioning Discipline
The work of actually switching a legacy system off, which is where migration savings are realised and which is routinely left undone.
Disposition Decision
Choosing one of the standard migration treatments for each application, on the basis of its value, condition and the constraint that is actually binding.
Dual Write
Writing the same change to both the old and new stores during a migration, and the reconciliation that makes it trustworthy.
ETL vs ELT
Whether data is transformed before loading into the target or after it, which decides where the compute happens and how much raw history you keep.
Lift and Shift
Moving an application to new infrastructure with minimal change, trading optimisation for speed and low migration risk.
Managed Service Substitution
Replacing a self-managed component with a managed equivalent during migration, without changing the application's architecture.
Operational Data Push
Sending modelled analytical data back into operational tools, which turns a warehouse table into a production dependency with none of the guarantees.
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.
Seam Identification
Locating the places in a legacy system where behaviour can be intercepted and redirected, which determines whether an incremental migration is feasible at all.
Slowly Changing Dimension
A strategy for handling attributes that change over time, deciding whether history is preserved and how facts attach to the correct version.
Star Schema
A dimensional model with one central fact table of measurements surrounded by denormalised dimension tables describing them.
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.
Sub-Second Aggregation Store
A database built to ingest continuously and answer aggregate queries over recent data in milliseconds, occupying the gap between OLTP and the warehouse.
Workload Fit Assessment
Choosing between warehouse, lake and lakehouse by the workloads that must run, rather than by which one is currently fashionable.
Leadership wants to consolidate a warehouse, a data lake and three departmental marts into a lakehouse. How do you scope and sequence this?
Establish the actual driver "Consolidate onto a lakehouse" is a solution. The driver is usually one of: cost of maintaining several copies, inconsistency betwee
A 15-year-old monolith must be modernised without a rewrite and without a feature freeze. Plan the migration.
Establish why, before deciding what "Modernise" is not an objective. The reasons that justify the cost are specific: delivery is too slow; the technology is uns
A CDC pipeline feeding your warehouse falls three hours behind during a source system's batch job, and the source's transaction log retention is 24 hours. What is the risk and what do you change?
The immediate risk Lag consumes the retention window. At three hours behind against a 24 hour retention, you have 21 hours of margin. If the consumer stops enti
A warehouse table now feeds the CRM through reverse ETL. It breaks, and the analytics team and the CRM team each say it is the other's problem. How do you resolve it?
The dispute is a design gap, not a personality problem A warehouse table built for analysis — nightly latency, best effort availability, schema changes made by
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
Production is degraded after a release. The team tries to roll back and discovers a migration has already run. What do you do now, and what do you change afterwards?
Now: stop trying to roll back Reverting the deployment would run the previous code against a schema it does not know, which is a second and less understood fail
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 choose between a cloud data warehouse and a lakehouse for a new analytics platform. How do you decide?
What actually differs The gap has narrowed considerably, so the decision turns on fewer things than the marketing suggests. Format ownership. In a lakehouse, da
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 must make a breaking change to an API used by 200 internal services and 40 external partners. Design the change and the migration.
First, verify it must break Many "breaking" changes are avoidable. Adding a field is safe if clients ignore unknown fields — which should be a documented expect
A finance report double-counts revenue after a new fact table is added. What is the likely modelling error?
The likely error: a fan out join between fact tables at different grains The classic mechanism. You have an order lines fact at line grain and a shipments fact
A release must rename a heavily used database column and ships tonight. The team proposes doing the rename in the deployment. What is wrong, and what do you propose?
What is wrong A rename is not additive. During a rolling deployment both versions of the application run simultaneously: one expects the old name, one the new.
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
Six weeks before launch, legal confirms that customer data for one market must be processed and stored in-country. The architecture is single-region in another jurisdiction. What do you do?
Establish exactly what the requirement covers Before designing anything, get three things in writing from legal: which data is in scope — usually a defined cate
Warehouse Migration
Moving off a legacy warehouse with thousands of reports pointed at it.
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.
Database Migration Under CD
Expand-contract, backwards-compatible schema change, and migrations that cannot roll back.
Migration Risk
Bounding blast radius, staging by cohort, and honest readiness reporting.
Warehouse, Lake & Lakehouse
Three answers to where analytical data lives, and the workloads that separate them.
Zero-Downtime Migration
Expand, migrate, contract — and the contract phase that never happens.
Embeddings
Dense representations, model coupling and the migration they imply.