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Terminology

2240 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 areas2240 Architecture Fundamentals77 Distributed Systems107 Data Architecture110 Cloud Architecture94 Networking88 API & Integration Architecture82 Reliability & Resilience80 Observability75 Performance & Capacity Engineering72 Security Architecture86 Cost Architecture & FinOps71 Business Architecture67 Architecture Communication67 Enterprise Architecture66 Legacy Modernization71 AI-Era Architecture74 Software Architecture & Engineering71 Architecture Patterns71 Architecture Decision-Making63 The Architect's Meta-Skills61 Delivery & Release Engineering66 Platform Engineering & Developer Experience70 Testing & Quality Architecture71 Data Platform Architecture69 Streaming & Real-Time Data69 Data Governance & Semantics74 Frontend & Experience Architecture66 Edge, Mobile & IoT68 Regulatory & Data Protection Architecture65 Assurance, Audit & Model Risk69
Kind Any concept806 practice738 pattern379 metric133 case-study77 tool62 protocol45

2240 terms shown.

Term Kind Topic What it is
Training-Serving Skew Online-Offline Skew, Feature Skew concept ML Platform A divergence between the features a model was trained on and the features computed at serving time - producing a model that performs well offline and worse in production, with nothing erroring.
Transaction Log Stream concept CDC to Stream Change events derived from a database's write-ahead log — faithful to the table's mutations and to its internal model rather than to the business's.
Transactional Audit Emission Audit in the Same Transaction, Complete Audit Guarantee practice Auditability Writing the audit record in the same transaction as the state change it describes, so that a crash cannot produce a change with no record - the property that distinguishes an audit trail from application logging.
Transactional Outbox Outbox Table, Reliable Event Publication, Store-and-Forward Events pattern Outbox Writing an event into a table within the same transaction as the business change, then publishing it separately - so the event exists if and only if the change committed, which no ordering of two independent w…
Transactional Outbox Outbox Pattern pattern Outbox Writing an event into the same database transaction as the state change, then relaying it, to eliminate the dual-write problem.
Transactions and Isolation ACID Isolation Levels concept Transactions & Isolation What a database guarantees when concurrent transactions touch the same data — and the anomalies each level permits.
Transfer Mechanism concept Cross-Border Transfer The specific legal instrument permitting personal data to leave a jurisdiction, which must exist per flow and which architecture must make identifiable.
Transformation Framework ELT Framework, SQL Transformation Tool tool Transformation Frameworks A tool that turns warehouse transformations into version-controlled, tested, dependency-aware code rather than a collection of scheduled scripts.
Trigger Condition Revisit Trigger, Decision Tripwire, Monitorable Assumption practice Deciding Under Uncertainty A specific, observable condition recorded alongside a decision that indicates it should be reconsidered - converting a point-in-time judgement into a monitorable position.
Trough-Based Commitment Baseline Reservation, Commit to the Floor practice Reserved & Committed Capacity Sizing reserved capacity to the quietest period rather than the average, because only the trough is capacity you are certain to use for the whole commitment term.
Trunk-Based Development TBD practice Branching Models All developers integrate small changes into a single shared branch at least daily, keeping it always releasable.
Trunk-Based Development in Practice practice Trunk-Based Development Everyone integrates to one shared branch at least daily, with incomplete work hidden behind flags rather than isolated in branches.
Trust Boundary Classification Where mTLS Is Required, Encryption Scope practice TLS & Certificates Writing down which network segments count as trust boundaries, so that mutual TLS is applied where it changes the security posture rather than uniformly or by intuition.
Trust Boundary Diagram practice Communicating Threat Models A diagram marking where data crosses between zones of differing trust, which is the structure a threat model is built on and the form security findings are best communicated in.
Try-Confirm-Cancel TCC, Reservation Pattern pattern Distributed Transactions A three-phase distributed transaction where each participant first reserves resources, and a coordinator then confirms or cancels all reservations.
TSB 2018: A Big-Bang Migration That Was Not Reversible TSB IT Migration case-study Cutover Planning A UK bank moved millions of customer accounts to a new platform in a single weekend cutover, and the failure locked customers out for weeks.
Twitter Timelines: Fan-Out on Write, Except for Celebrities Timeline Fan-Out, Hybrid Fan-Out case-study Materialized Views Precomputing every user's timeline at write time is fast to read and impossible for accounts with millions of followers, so the two approaches are combined.
Twitter's Timeline Fan-Out case-study Performance & Capacity Twitter precomputes each user's timeline at write time but handles very-high-follower accounts at read time, because neither strategy alone survives both ends of the distribution.
Two-Phase Commit 2PC, XA protocol Distributed Systems A blocking protocol for atomic commit across several resources: a coordinator asks all participants to prepare, then tells them all to commit or abort.
Two-Phase Locking 2PL protocol Transactions & Isolation The concurrency control protocol behind serializable isolation — acquire locks in a growing phase, release only in a shrinking phase, never interleaving the two.
Two-Pizza Team concept Business Architecture Amazon's heuristic that a team should be small enough to be fed by two pizzas, and — the substantive part — should own its service end to end.
Two-Stage Retrieval pattern Reranking Retrieving a broad candidate set cheaply and then reordering it with an expensive, more accurate model.
Two-Way Door concept Reversibility A decision that can be undone cheaply, and which therefore warrants a fast decision by the people closest to the work rather than extensive analysis.
Uber DOMA: Structure Above Microservices Domain-Oriented Microservice Architecture case-study Microservices Having reached thousands of microservices, Uber introduced domains and layers above them because independent services had recreated the coordination problem they were meant to solve.
Uber H3: Hexagonal Spatial Indexing H3, Hexagonal Hierarchical Index case-study Indexing Uber built and open-sourced a hexagonal grid index because uniform neighbour distance matters when you are analysing supply and demand across space.
Uber's Domain-Oriented Microservice Architecture DOMA case-study Software Architecture After growing to roughly 2,200 microservices, Uber grouped them into domains behind gateways with strict dependency layering, to recover the comprehensibility that fine-grained decomposition had cost.
Uber's H3 Spatial Index case-study Data Architecture Uber indexes the world with hexagons rather than squares, because uniform neighbour distance makes supply, demand and pricing computations correct as well as fast.
Uber: Choosing a Database for Write Amplification Uber Postgres to MySQL case-study Technology Selection Uber publicly documented moving from Postgres to MySQL for their workload, and the reasoning is a useful lesson in evaluating a datastore against your actual access pattern.
Ubiquitous Language practice Domain-Driven Design A shared vocabulary used identically by domain experts and in the code, so that translation between business and implementation is unnecessary.
UI Monorepo Strategy practice UI Monorepo Strategy Whether frontend code lives in one repository or many — a trade between atomic change and independent release.
Unbounded Dataset concept Streaming & Real-Time Data Input with no known end, which removes the option of waiting for completeness and forces every aggregate to be provisional.
Unbundled Event Store Disaggregated Telemetry Store, Object-Storage Column Store pattern Real-Time Analytical Stores A telemetry store that separates writing, compaction and querying into independently scaled services over shared object storage and a metadata store, so retention cost stops being tied to the size of the query…
Unenforced Standard Paper Standard, Decorative Governance concept Influence Without Authority A written rule with no mechanism behind it - an anti-pattern whose cost is paid per decision in argument and divergence work while compliance stays partial and uniformity is never achieved.
Unfunded Technical Consequence Business-Model Debt, Structural Liability, Implied Requirement concept Business Capabilities A computational or operational difficulty implied by a business-model decision but never costed, because the decision was evaluated on commercial merits in a conversation the technical consequence was not part of.
Unintentional Transfer Incidental Transfer, Shadow Data Flow concept Cross-Border Transfer Personal data crossing a jurisdictional boundary through a path nobody classified as a transfer - telemetry, support access, backups, or a processor's staff - which is what audits actually find.
Unit Cost Ceiling Cost per Transaction Limit, Infrastructure Cost Budget per Order metric Business Understanding The infrastructure cost per transaction that the business model can bear, derived from contribution margin and fixed before design, which decides how much work a request is allowed to do.
Unit Economics metric Unit Economics Infrastructure cost expressed per unit of business value delivered, which reveals efficiency trends that absolute spend cannot.
Unit Economics of a System metric Unit Economics The cost to serve one unit of business value — a customer, an order, a request — which determines whether a system's economics improve or worsen with scale.
Universal Scalability Law USL, Gunther's Law concept Horizontal vs Vertical Scaling A model showing that throughput rises with concurrency, flattens due to contention, and then falls due to coherency costs.
Unmanaged Change Surface Out-of-Band Change Path, Ungated Change concept Deployment Gates Every mechanism that can alter production without passing through the deployment pipeline - so the organisation's rollout controls apply to a fraction of its changes and the incidents come from the rest.
Unmerge Capability Merge Reversal, Split-Back pattern Master Data Management The designed ability to reverse an incorrect entity merge and restore both original records, which requires that source keys and pre-merge attribute values were never destroyed.
Unreachable Node concept Edge, Mobile & IoT A component you cannot log into, restart or inspect, which removes every operational technique that assumes access to the running system.
Untrusted Build Step Third-Party CI Step, Curl-Pipe-Shell Step concept Pipeline Secrets Any pipeline step whose code you do not control and did not review - a downloaded script, a third-party action, a plugin - which runs with the whole job's credentials and network access.
Untrusted Client Timestamp Device Time Is Not Authoritative, Client Clock Assumption concept Mobile App Architecture The recognition that a timestamp set by a device is user-editable input rather than a fact - so reporting periods, ordering and de-duplication must not depend on it.
Update Cadence Commitment Next-Update Promise, Incident Comms Rhythm practice Presenting to Executives Promising when the next update will arrive rather than when the problem will be fixed, so the one commitment made during an incident is one the team can actually keep.
Update Long Tail Version Distribution Tail, Fleet Stratification concept OTA Updates The persistent stratum of devices running old firmware because they were offline during rollouts - which grows across releases and is measured by version distribution rather than by rollout percentage.
Usage Telemetry Who Calls This, Consumer Visibility practice Platform Telemetry Per-capability, per-consumer usage data about a platform's own surfaces - the precondition for every deprecation, roadmap and change-impact decision a platform team makes.
Usage-Based Access Review Last-Used Entitlement Review, Evidence-Based Access Recertification practice Identity & Access Management Recertifying entitlements against observed use rather than against manager approval, so unused permissions are removed by default instead of being re-approved by someone who cannot evaluate them.
Use Case Risk Classification practice AI Risk Tiering Assigning an AI application to a risk tier based on the consequence of it being wrong, which then determines the obligations that apply.
USE Method practice Observability For every resource, track Utilisation, Saturation and Errors — the resource-centric complement to request-centric monitoring.
Use-Time Enforcement Check at the Point of Use, Consent as a Service concept Consent Architecture Checking permission at the moment data is used rather than at the moment it is collected, because a copied permission flag is stale the moment it is made.
User Journey SLO Critical User Journey, CUJ practice SLI, SLO & SLA Defining reliability targets around what a user is trying to accomplish, measured where the user is, rather than around per-request success rates at the server.
Utilisation and Queueing Delay concept Queueing Theory The non-linear relationship by which waiting time grows as utilisation approaches one, explaining why systems degrade suddenly rather than gradually.
Utilisation Break-Even Break-Even Utilisation, Execution Model Crossover metric Serverless vs Containers The sustained busy fraction at which always-on compute becomes cheaper than per-invocation billing, which turns the serverless-or-containers argument into arithmetic instead of preference.
Utilisation Floor metric Rightsizing The minimum utilisation a resource should sustain before it is considered over-provisioned, set with enough margin for failure and peak.
Utilisation Target practice Queueing Theory The operating point chosen from a latency requirement rather than from cost efficiency, because queueing delay rises non-linearly as utilisation approaches saturation.
Utility Tree practice Quality Attributes A structured decomposition of quality attributes into concrete, prioritised scenarios, used to focus architectural analysis on what actually matters.
Vacuous Pass Assertion-Free Test, Empty-Set Pass, Silent Test concept Testing & Quality Architecture A test that passes because it verified nothing rather than because the code is correct - an assertion that never ran, a loop over an empty collection, a mock that could not fail - which is worse than having no…
Validated Envelope Model Use Envelope, Validation Boundary concept Model Risk Management The explicit conditions a model's validation actually covers - input schema, population, feature sources, thresholds, upstream versions - outside which the sign-off does not hold and the serving path must refu…
Value Stream concept Business Architecture The end-to-end sequence of activities that delivers a result to a customer, viewed across whatever departments and systems it happens to cross.