Search the practice set
126 questions, 454 terms and 400 topics in 20 areas.
60 results for “Legacy Integration”
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.
Enterprise Integration Patterns
A catalogue of named, composable messaging patterns — router, translator, aggregator, splitter, filter, dead letter channel — that gives integration work a shared vocabulary.
Event-Driven Integration
Systems integrating by publishing and consuming events rather than by calling each other's APIs.
API Gateway
A single entry point in front of a set of services that handles authentication, rate limiting, routing and protocol translation.
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.
Backward Compatibility
The property that a new version of a producer continues to work with clients written against the old version.
CI/CD
Merging work continuously into a shared trunk with automated verification, and keeping every commit in a state that could be released.
Change Data Capture
Publishing a stream of a database's row-level changes by reading its replication log, without modifying the application that owns it.
Contract Testing
Verifying that a provider satisfies the expectations each of its consumers actually relies on, without running all the services together.
Dead Letter Queue
A separate queue that receives messages which could not be processed after a set number of attempts, so they neither block the consumer nor disappear.
GraphQL
A query language and runtime where the client specifies exactly which fields it needs, against a typed schema, usually via a single endpoint.
Idempotency Key
A client-generated unique value sent with a request so the server can recognise a retry and return the original result instead of acting twice.
LinkedIn and the Origin of Kafka
Kafka was built to replace point-to-point data integration between many systems with a single durable log that any system could publish to and any number could read.
Model Context Protocol
An open protocol that standardises how AI applications connect to external tools, data sources and prompts.
OpenAPI
A machine-readable specification format for HTTP APIs, from which documentation, clients, servers, mocks and validation can be generated.
Parallel Run
Running the old and new systems side by side on the same inputs and comparing outputs, before the new one is trusted.
REST
An architectural style for APIs built on resources identified by URLs, manipulated with uniform HTTP methods, and stateless requests.
Rate Limiting
Bounding how many requests a caller may make in a window, to protect capacity and enforce fair use.
Re-architect vs Rebuild
Restructuring an existing system incrementally versus writing a replacement from scratch — and the strong evidence that incremental wins.
Run a threat model on a new payment integration: our service calls a third-party payment provider and receives webhooks. Where are the interesting threats?
Draw the boundaries first Three trust boundaries, and nearly every interesting threat lives on one of them: 1. User → our service (untrusted input, authenticate
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 downstream team needs to react to order changes. The order service can publish events, or they can consume CDC from its database. Which, and why?
The recommendation: published events, with CDC as the mechanism if needed The distinction that matters is what the consumer becomes coupled to . CDC consumed di
A service writes to its database and then publishes an event to Kafka. Sometimes consumers see an event for a record that does not exist, and sometimes a record exists with no event. Why, and how do you fix it?
What the interviewer is testing Recognition of the dual write problem — one of the most common defects in event driven systems and one that testing rarely catch
An order service must notify inventory, billing, shipping and analytics when an order is placed. Synchronous calls or events? Justify your choice per consumer.
What the interviewer is testing Whether you apply the decision per interaction rather than adopting one style globally. The framing that matters Synchronous cal
Legacy Integration
Reaching systems that cannot change, without importing their model.
Legacy Integration Patterns
Anti-corruption layers, adapters and CDC against systems that cannot change.
API & Integration
General material on integrating systems through contracts.
Enterprise Integration
Estate-wide integration strategy, standards and shared infrastructure.
Event-Driven Integration
Publishing facts rather than commands, and versioning event schemas.
Integration Patterns
Routers, translators, splitters, aggregators and dead letter channels.
Legacy Assessment
Understanding what a system does before deciding what to do with it.
Legacy Modernization
General material on modernising existing systems.
Partner & B2B Integration
External contracts, onboarding, sandboxes and long deprecation windows.
API Documentation
OpenAPI as a machine-checked contract rather than as prose.
API Error Handling
Error shapes, retryability signals and machine-readable causes.
API Versioning
URL, header and account-pinned versioning, and who carries the burden.
APIs as Products
Ownership, lifecycle, deprecation policy and developer experience.
Application Decomposition
Finding seams in a monolith, starting from the data.
Backward Compatibility
Which changes are safe, and how to make breakage a build failure.
CI/CD
Continuous integration and delivery, and the architecture that caps them.
Coexistence Patterns
Running old and new together for years without corrupting either.
Contract Testing
Verifying what consumers actually rely on, without a shared environment.
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.
GraphQL
Client-specified queries, N+1 resolution and query-cost control.
Idempotency Keys
Client-generated keys stored atomically with the operation they guard.
Mainframe Modernization
Batch windows, COBOL, and the risk profile of core banking systems.
Message Formats
JSON, Protobuf, Avro — schema evolution and payload economics.
Migration Risk
Bounding blast radius, staging by cohort, and honest readiness reporting.
Modernisation Business Case
Pricing tail risk so deferred maintenance becomes fundable.
Pagination & Filtering
Offset versus cursor, stable ordering and unbounded result sets.
Parallel Run
Shadowing the old system to discover the rules nobody documented.
REST Design
Resources, uniform methods, status codes and statelessness.
Rate Limiting
Algorithms, shared counters, and signalling rejection properly.
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.