Terminology

2205 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 areas2205 Architecture Fundamentals77 Distributed Systems107 Data Architecture110 Cloud Architecture94 Networking88 API & Integration Architecture82 Reliability & Resilience75 Observability70 Performance & Capacity Engineering72 Security Architecture86 Cost Architecture & FinOps71 Business Architecture67 Architecture Communication67 Enterprise Architecture66 Legacy Modernization71 AI-Era Architecture69 Software Architecture & Engineering71 Architecture Patterns71 Architecture Decision-Making63 The Architect's Meta-Skills61 Delivery & Release Engineering66 Platform Engineering & Developer Experience70 Testing & Quality Architecture66 Data Platform Architecture64 Streaming & Real-Time Data69 Data Governance & Semantics69 Frontend & Experience Architecture66 Edge, Mobile & IoT68 Regulatory & Data Protection Architecture65 Assurance, Audit & Model Risk64

Kind Any concept794 practice734 pattern368 metric125 case-study77 tool62 protocol45

794 terms shown.

Term	Kind	Topic	What it is
Temporal Coupling	concept	Coupling	A dependency in which one component requires another to be available at the same moment, so the availability of both is required for either to work.
Terraform State IaC State File	concept	Infrastructure as Code	The file mapping declared resources to real infrastructure, without which the tool cannot tell what it already created — and which becomes critical infrastructure in its own right.
Test Double Boundary	concept	Integration Test Boundaries	The line inside a test between what is real and what is substituted, which determines exactly what the test can and cannot prove.
Test Strategy Altitude	concept	Testing & Quality Architecture	Deciding which risks are verified at which level, so that each layer tests something the layers below it structurally cannot.
Testability Design for Test	concept	Testing & Quality Architecture	The architectural property that determines what kinds of test are possible - which decides the shape of the suite far more than any testing discipline does.
Testability as a Design Property	concept	Test Architecture Strategy	How cheaply a system's behaviour can be observed and controlled, which is decided by architecture and largely fixed before any test is written.
Testing Strategy Shape	concept	Testing Strategies	The distribution of tests across levels, chosen so that feedback is fast where it can be and confidence is real where it must be.
Testing Trophy	concept	Test Pyramid Shapes	A distribution weighted towards integration tests rather than unit tests, appropriate where most of the risk lives at boundaries rather than in logic.
Theory of Constraints	concept	Constraint Thinking	The principle that a system's throughput is set by a single binding constraint, so improvement anywhere else produces nothing.
Threat Model Trust Boundary	concept	Threat Modelling	The line across which data or control passes from a less trusted context to a more trusted one, and where validation and authorisation must occur.
Three Lines Model Three Lines of Defence	concept	Three Lines Model	The organisational separation between those who own and manage risk, those who oversee and challenge, and those who provide independent assurance.
Thundering Herd	concept	Distributed Systems	A large number of clients acting simultaneously because they were synchronised by a shared event, producing a spike that the steady-state design never sized for.
Ticket Ops Ticket-Driven Operations	concept	Self-Service Provisioning	An operating model where teams obtain infrastructure and change by requesting it from another team, making that team a queue.
Time to Market	concept	Time to Market	How long from idea to customer value — an architectural property determined by coupling, batch size and the number of teams required.
Time Travel Data Versioning, Snapshot Query	concept	Data Lakes & Lakehouses	Querying a table as it existed at a previous version or timestamp, made possible by keeping the metadata and files of prior commits.
TLS Termination Boundary Encryption Termination Point, Decryption Boundary	concept	Network Security	The exact point where ciphertext becomes plaintext, which is the real answer to "is data encrypted in transit" - everything past it travels in the clear on a wire somebody owns.
Toil	concept	Reliability Culture	Manual, repetitive, automatable operational work that scales linearly with the size of the service and produces no lasting improvement.
Token Domain Entropy Tokenised Value Space, Surrogate Input Entropy	concept	Tokenisation & Masking	The size and guessability of the value space a deterministic token is computed from, which decides whether that token is a usable pseudonym or a lookup key an attacker can rebuild without ever touching the vault.
Token Revocation Gap	concept	Tokens & JWTs	The window between deciding a token should no longer be valid and it actually ceasing to work, which for self-contained tokens is its remaining lifetime.
Tombstone Accumulation Metadata Growth, CRDT Garbage Problem	concept	CRDTs	The unbounded growth of deletion markers and causal metadata that a coordination-free replica must retain so a peer it has not yet seen cannot resurrect removed data.
Tool Authorisation Boundary Model as Untrusted Proposer, Authorise Outside the Model	concept	Prompt Injection Defence	Authorising every tool invocation against the initiating user's own permissions, outside the model - because the model cannot distinguish instructions from data and no prompt-level defence is reliable.
Total Cost of Ownership TCO	concept	Total Cost of Ownership	The full lifetime cost of a choice — infrastructure, licences, and the engineering time that is usually the largest term and the one omitted.
Toxic Combination	concept	Segregation of Duties	A pair of permissions that is acceptable individually and dangerous together, which is what a segregation-of-duties model exists to identify.
Trade-off Fundamentals	concept	Trade-off Fundamentals	Every architecture is a set of purchases; the skill is naming what was bought, what was sold, and at what exchange rate.
Trade-off Surface	concept	Trade-off Analysis	The set of achievable combinations of competing qualities, on which improving one attribute necessarily costs another.
Traffic-Mix Skew Canary Population Bias, Assignment Bias	concept	Testing in Production	A canary or experiment arm receiving a population that differs systematically from the baseline - so the comparison measures who was routed rather than what changed.
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.
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.
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-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.
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.
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.
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.
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 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.
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.
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.
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.
Value Streams	concept	Value Streams	The end-to-end sequence from a customer's trigger to their outcome — the frame that shows whether teams are aligned to flow or to function.
Vendor Lock-In	concept	Technical Constraints	The cost of switching away from a provider, treated as a quantity to be managed deliberately rather than a condition to be avoided absolutely.
Version Vector Vector Clock	concept	Clocks & Ordering	A per-replica counter set that lets a system tell whether one version causally descends from another or whether the two are genuinely concurrent.
View Staleness Window	concept	Materialized Views	The maximum age of data in a precomputed view, which must be an explicit, monitored contract rather than an incidental property.
Virtual Private Cloud VPC, VNet	concept	Networking	A logically isolated network inside a cloud provider, with an address range you control and explicit rules for what may enter and leave.
Visibility Timeout Message Lease, Invisibility Window	concept	Competing Consumers	The period a claimed message is hidden from other consumers - too short and work is duplicated, too long and a crashed worker stalls the item.
Voluntary Adoption Pull-Based Adoption, Chosen Uptake, Non-Mandated Usage	concept	Platform Adoption	Usage of a platform by teams that could have chosen otherwise - which is the only measurement that indicates whether the platform is actually useful, and which a mandate permanently destroys.
VPC Peering	concept	VPC Design	A direct network connection between two VPCs, which is simple, cheap and non-transitive — the last property being the one that shapes topology.
VPN vs Dedicated Connection Direct Connect, ExpressRoute	concept	Private Connectivity	Two ways to link on-premises networks to cloud — an encrypted tunnel over the internet, or a private physical circuit.
Wall-Clock Schedule Hazard Local-Time Trigger Hazard, DST Schedule Ambiguity	concept	Batch Orchestration	The class of batch faults caused by triggering work on a civil clock that repeats, skips or shifts, producing duplicate or missing runs that no job reports as an error.
Warehouse Concurrency Scaling	concept	Workload Isolation	Adding compute clusters to absorb concurrent queries rather than queueing them, and the cost behaviour that turns a queue into a bill.
Warn-Mode Debt Advisory Gate Backlog, Non-Blocking Policy Debt	concept	Architecture Compliance Checks	The accumulated violations of a policy that has only ever warned, which makes switching it to blocking politically impossible and hides how many of its rules are simply wrong.
Watermark Event-Time Progress, Completeness Estimate, Lateness Boundary	concept	Watermarks & Late Data	A heuristic assertion that no further events earlier than a given event time are expected, which is how a stream processor decides when a window is complete - and therefore where the correctness-versus-promptn…
Watermark	concept	Watermarks & Late Data	The stream processor's assertion that no further events older than a given event time are expected, which is what allows a window to close.
Webhook Retry Policy	concept	Webhooks	The provider's schedule for re-attempting failed deliveries, and the contract the receiver must be built against.