Terminology

791 terms, tools, patterns and metrics an architect is expected to use precisely. Each one gets a short explanation of what it is, and — where it matters — what it is commonly confused with. Search filters as you type; the column headers sort.

All areas791 Architecture Fundamentals38 Distributed Systems73 Data Architecture71 Cloud Architecture55 Networking51 API & Integration Architecture45 Reliability & Resilience40 Observability33 Performance & Capacity Engineering34 Security Architecture50 Cost Architecture & FinOps30 Business Architecture28 Architecture Communication27 Enterprise Architecture27 Legacy Modernization27 AI-Era Architecture34 Software Architecture & Engineering37 Architecture Patterns34 Architecture Decision-Making30 The Architect's Meta-Skills27

Kind Any concept292 practice240 pattern133 metric36 protocol32 tool32 case-study26

791 terms shown.

Term	Kind	Topic	What it is
Prompt Versioning	practice	AI-Era Architecture	Treating prompts as versioned, reviewed, tested artefacts rather than as strings edited in place.
Protocol Buffers Protobuf	protocol	gRPC Transport	A binary serialisation format with a schema definition language, generating typed code and enforcing explicit compatibility rules through field numbering.
Provider Verification	practice	Contract Testing	The provider-side stage that replays every consumer's recorded expectations against the real implementation.
Provisioned vs Serverless Capacity	concept	Cloud Databases	Paying for a fixed database size continuously, versus paying for capacity consumed with automatic scaling — a crossover decision driven by duty cycle.
Proxy Buffering	concept	Reverse Proxies	Whether a reverse proxy accumulates a response before forwarding it, which protects the backend from slow clients but breaks streaming.
Publish/Subscribe Pub/Sub	pattern	Architecture Patterns	A messaging pattern where each published message is delivered to every interested subscriber, rather than to one competing worker.
Purpose Limitation	concept	Privacy Engineering	The principle that personal data collected for one stated purpose may not be used for an unrelated one without a new lawful basis.
Quality Attribute Scenario QAS	practice	Architecture Fundamentals	A structured, testable statement of a non-functional requirement: source, stimulus, environment, artefact, response, response measure.
Query Plan Execution Plan, EXPLAIN	concept	Data Architecture	The database's chosen strategy for executing a query, and the first thing to look at when one is slow.
Query Plan Regression	concept	Database Performance	A sudden latency increase caused by the database optimiser choosing a different execution plan for an unchanged query, typically after statistics or data volume change.
Query-Based CDC Polling CDC, Timestamp-Based CDC	pattern	Change Data Capture	Detecting changes by repeatedly querying for rows modified since the last run — simple, universally available, and lossy in specific ways.
Queue Length Estimation	practice	Little's Law	Using the relationship between arrival rate, residence time and items in the system to size pools, predict backlogs and sanity-check capacity claims.
QUIC HTTP/3	protocol	HTTP/1.1, HTTP/2 & HTTP/3	A transport built on UDP that provides streams, encryption and congestion control, removing TCP's head-of-line blocking and reducing connection setup latency.
Quorum	concept	Distributed Systems	A minimum number of nodes that must acknowledge an operation for it to count, chosen so that read and write sets are guaranteed to overlap.
Radar Ring Semantics	practice	Technology Radar	The meaning attached to each ring of a technology radar, which determines whether it guides decisions or merely lists opinions.
Raft	protocol	Consensus Protocols	A consensus algorithm designed to be understandable, decomposing agreement into leader election, log replication and safety.
Rate Limiting	pattern	API & Integration	Bounding how many requests a caller may make in a window, to protect capacity and enforce fair use.
Re-architect vs Rebuild	concept	Legacy Modernization	Restructuring an existing system incrementally versus writing a replacement from scratch — and the strong evidence that incremental wins.
Reactive Streams	protocol	Backpressure & Flow Control	A specification for asynchronous stream processing in which the consumer requests a specific number of items, making backpressure part of the protocol rather than an afterthought.
Read Model Query Model, Projection Store	pattern	CQRS	A data structure shaped for a specific query rather than for the domain, maintained separately from the write model.
Read Model Projection	pattern	CQRS	A denormalised store built and maintained from write-side events specifically to serve one query shape efficiently.
Read Replica	pattern	Data Architecture	A copy of a database that receives changes from the primary and serves read-only queries, spreading read load.
Read Timeout Socket Timeout	concept	Timeouts & Deadlines	The bound on how long a client waits for response data after a connection is established — distinct from the connect timeout, and the one that usually matters.
Read-Your-Writes Consistency Read-After-Write	concept	Consistency Models	A session guarantee that a client always sees its own updates, even when reads are served from replicas that may lag.
Rearchitecture Threshold	concept	Refactoring & Re-architecting	The conditions under which rebuilding a system is justified, given that it is the most expensive treatment and is chosen far more often than it is warranted.
Recovery Point Objective RPO	metric	RTO & RPO	The maximum acceptable data loss measured as a duration, determining the replication and backup strategy.
Recovery Time Objective RTO	metric	RTO & RPO	The maximum acceptable duration between a failure and restored service, agreed with the business rather than chosen by engineering.
RED Method	practice	Observability	A minimal per-service dashboard: Rate, Errors, Duration — the request-centric view of whether users are being served.
Redlock	protocol	Distributed Locking	An algorithm for distributed locking across independent Redis instances, and the subject of a well-known critique about what locks can guarantee at all.
Redundancy	concept	Reliability & Resilience	Having more instances of a component than the load requires, so that failures can be absorbed without loss of service.
Refactoring	practice	Software Architecture	Changing the internal structure of code without changing its external behaviour, in small verified steps.
Refactoring Under Test	practice	Refactoring	Changing internal structure without changing behaviour, with tests as the mechanism that makes the claim verifiable.
Reference Architecture	practice	Enterprise Architecture	A pre-approved, documented template for a recurring class of solution, so that similar problems do not get individually redesigned.
Reference Implementation	practice	Reference Architectures	A working example of a reference architecture that teams can run, read and copy, as opposed to a document describing one.
Refresh Token	concept	Tokens & JWTs	A long-lived credential used solely to obtain new short-lived access tokens, so sessions can persist without long-lived access tokens circulating.
Region Selection Criteria	practice	Single vs Multi-Region	The factors determining where workloads run, in which data residency and latency usually dominate cost.
Regional Evacuation Region Failover Drill	practice	Multi-Region Architecture	The deliberate, rehearsed act of shifting all traffic out of a region — treated as a routine operation rather than an emergency procedure.
Regulatory Constraint	concept	Business Architecture	A legal requirement that removes design options — and one that must be established early, because it is not negotiable and is expensive to retrofit.
Reliability Headroom	metric	Capacity Planning	The gap between provisioned capacity and the load that would be carried after the largest planned failure, measured under peak conditions.
Replatform Lift and Reshape	practice	Legacy Modernization	Migrating an application largely as-is while making targeted changes to exploit the target platform — usually the best return per unit of effort.
Replication Lag	metric	Replication	How far behind a replica is, measured in time or in log position — the quantity that determines how stale a replica read can be.
Request-Based and Window-Based SLI	metric	SLI, SLO & SLA	Two ways of computing the same reliability target — counting good events, or counting good time windows — which produce materially different numbers.
Request-Reply and Fire-and-Forget	concept	Sync vs Async	The two interaction shapes available between components, differing in whether the caller waits for a result and therefore in whether availability compounds.
Resource Modelling	practice	REST Design	Expressing an API as nouns with a consistent hierarchy rather than as verbs, so URLs are predictable and methods carry the semantics.
Resource Requests and Limits	concept	Kubernetes	The declared minimum a container is guaranteed (request) and the maximum it may consume (limit) — the two numbers that determine scheduling, packing and throttling.
Resource Saturation Audit	practice	Bottleneck Analysis	A systematic checklist for locating resource bottlenecks by examining utilisation, saturation and errors for every resource in the system.
REST RESTful API	protocol	API & Integration	An architectural style for APIs built on resources identified by URLs, manipulated with uniform HTTP methods, and stateless requests.
Restore Drill	practice	Backup Strategies	A scheduled, timed exercise of restoring from backup into a clean environment — the only thing that converts a backup from a hope into a control.
Restore Verification	practice	DR Testing	Periodically performing a real restore from backup and validating the result, as the only evidence that a recovery capability exists.
Retrieval Pipeline Stages	pattern	RAG Architecture	The stages that turn a user question into grounded context — query processing, retrieval, reranking and assembly — each independently tunable.
Retrieval-Augmented Generation RAG	pattern	AI-Era Architecture	Retrieving relevant documents at query time and putting them in the model's context, so answers are grounded in your data rather than in training data.
Retry Budget	pattern	Retries & Backoff	Capping retries as a proportion of overall traffic rather than as a count per request, so retries cannot multiply during the failure they are meant to survive.
Retry-After	protocol	Rate Limiting	A response header telling a client how long to wait before retrying, turning a rejection into actionable guidance.
Retryable Error	concept	API Error Handling	An error whose cause may resolve on its own, which a client may safely attempt again — as distinct from one that will fail identically.
Reverse Proxy	pattern	Networking	A server that receives client requests on behalf of one or more backends, forwarding them and returning the response.
Reversibility	concept	Trade-off Fundamentals	The property of a decision that determines how much analysis it deserves, since a cheaply reversible choice can be tested rather than debated.
Reversible Decision Two-Way Door	concept	Architecture Decision-Making	A choice that can be undone cheaply, and which therefore deserves far less deliberation than an irreversible one.
Review Latency	metric	Code Review	The time between a change being ready for review and the review happening, which is usually the largest component of lead time.
Review Readiness Criteria	practice	Architecture Reviews	A stated bar a design must meet before review, so the session is spent on judgement rather than on discovering that the work is not ready.
Right to Erasure Right to be Forgotten	concept	Data Lifecycle & Retention	A data subject's right to have their personal data deleted, and an obligation that reaches every copy an architecture has created.