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
Escape Hatch Drop to Primitives, Graduated Abstraction, Opt-Out Path	concept	Abstraction Level Choice	A supported way for a team to bypass part of a platform abstraction and work with the underlying primitives - which is what makes an abstraction safe to adopt and what supplies the platform's most valuable roa…
Ethics in Architecture	concept	Ethics in Architecture	The consequences of architectural decisions for people who did not choose them — and the architect's responsibility for the ones that are foreseeable.
ETL vs ELT	concept	Data Architecture	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.
Event Notification vs Event-Carried State	concept	Event-Driven Integration	Whether an event carries only the fact that something happened, or also the data a consumer needs to act on it.
Event Time Versus Processing Time	concept	Windowing	The distinction between when something happened and when the system saw it, which determines whether results are reproducible.
Event Time vs Processing Time	concept	Windowing	The distinction between when something happened in the world and when the system got round to handling it.
Eventual Consistency	concept	Distributed Systems	A guarantee that replicas will converge to the same value if updates stop, with no bound on how long reads may be stale.
Evidence Transferability Context Matching, Scale Applicability, Case Study Fit	concept	Explaining Trade-offs	The degree to which a finding from another organisation's system applies to yours, determined by similarity of workload shape, scale and constraints - and the discipline of extracting the question rather than …
Evolutionary Architecture	concept	Evolutionary Architecture	Designing for guided incremental change rather than for a correct end state, because the requirements that will matter most are not yet known.
Exactly-Once Semantics EOS, Effectively-Once	concept	Exactly-Once Semantics	The guarantee that each input record affects the output state precisely once, achieved through atomic state-and-offset commits rather than through delivering messages once.
Exception Tail Long Tail of Cases, Manual Remainder	concept	Business Processes	The minority of cases an automated process cannot handle, whose automation cost per case rises steeply, so the economically correct end state is usually a smaller manual path rather than none.
Exception Union Requirements Union, Consolidation Scope Creep	concept	Application Rationalisation	The failure mode of consolidation programmes in which the replacement system inherits the union of every source system's local exceptions, making it more complex than any system it replaces.
Execution Model Fit	concept	Serverless vs Containers	Matching a workload's traffic shape, duration and state requirements to the execution model that suits it, rather than choosing one model for everything.
Exemplar	concept	OpenTelemetry	A trace identifier attached to a metric data point, linking an aggregate measurement directly to a concrete request that produced it.
Exit and Concentration Risk	concept	Exit & Concentration Risk	The regulatory concern that an institution cannot leave a critical provider, and that too much of the sector depends on the same few providers.
Expensive-to-Change Core	concept	Delivery vs Maintainability	The small part of a system whose shape is copied into stored data and into other people's code, where a shortcut cannot be repaid locally - so deliberate debt belongs everywhere else.
Fact Grain Multiplication Join Fan-Out, Dimension Row Explosion	concept	Slowly Changing Dimensions	Silent duplication of fact rows when a fact is joined to a versioned dimension without an effective-date predicate, inflating every additive measure in proportion to how often dimension members change.
Fail-Fast vs Fail-Safe	concept	Failure Modes	Whether a component should stop immediately on detecting a problem, or continue in a degraded but safe mode — a choice that depends entirely on which outcome is worse.
Failure Threshold	concept	Circuit Breakers	The condition that trips a circuit breaker — best expressed as a failure rate over a rolling window with a minimum request volume, not as a consecutive-failure count.
Fairness Definition Choice Incompatible Fairness Metrics, Which Fairness	concept	Bias & Fairness Controls	The unavoidable selection between mathematically incompatible fairness definitions - a legal and business determination that a team makes implicitly if it does not make it explicitly.
Fairness Through Unawareness Blindness Approach, Attribute Removal	concept	Bias & Fairness Controls	The mistaken belief that removing a protected attribute from a model's inputs prevents disparate outcomes, when correlated features still carry the attribute and the deletion usually destroys the ability to me…
Fake Drift Virtualisation Divergence, Stale Mock	concept	Service Virtualisation	The divergence between a simulated dependency and the real one it stands in for - which makes tests pass while the real integration fails, producing confidence rather than caution.
False Analogy	concept	Pattern Recognition	Applying a pattern learned in one context to a superficially similar situation whose relevant properties differ.
Fan-Out	concept	Distributed Systems	One incoming request causing many outgoing ones, which multiplies both load and tail latency.
Fan-Out Amplification Broadcast Multiplication, Subscriber Amplification	concept	WebSockets & Realtime	The property that one input event becomes as many output events as there are subscribers, making the workload proportional to audience size rather than to event rate - and the reason broadcast paths cannot sha…
Fan-Out Latency Amplification	concept	Tail Latency	The effect by which a request that depends on many parallel sub-requests is governed by the slowest of them, so rare slowness becomes common at the user level.
Fan-out on Write vs Fan-out on Read Push vs Pull Timelines	concept	Messaging & Queues	Whether an event is copied to every recipient's store at publish time, or assembled from sources at read time - and why large systems need both.
Fault Domain	concept	Fault Isolation	A boundary within which a single failure is contained, defined by the infrastructure and dependencies that components inside it share.
Fault Tolerance	concept	Distributed Systems	Continuing to operate correctly despite the failure of some components, by design rather than by luck.
Feature Parity Trap	concept	Rebuild vs Re-architect	The expectation that a replacement system must match every behaviour of the old one before it can be adopted, which is what makes rewrites never finish.
Feedback Loop	concept	Systems Thinking	A circular causal chain in which an effect influences its own cause, producing behaviour that cannot be understood by examining components in isolation.
Field Data Versus Lab Data	concept	Real User Monitoring	The difference between what real users on real devices experience and what a synthetic run measures, and why the second is systematically optimistic.
Filter Composability	concept	Pipes and Filters	The property that makes a pipeline style work — each stage transforms input to output with no shared state, so stages can be reordered, reused and scaled independently.
Financial Services Regulation	concept	Financial Services Regulation	Architecture under financial regulation — where record-keeping, demonstrable resilience, and the ability to exit a provider are structural requirements.
Firewalls and Security Groups	concept	Firewalls & Security Groups	Network-level access control, its real value as a second layer, and why the perimeter model stopped being sufficient.
Fitness Function Drift Vacuous Check, Silent Rule Decay	concept	Fitness Functions	The failure mode in which an architecture check keeps passing after it has stopped examining anything, so a green build certifies a rule that is no longer enforced.
Flag Debt	concept	Feature Flags	The accumulating complexity of feature flags that are never removed, producing untested code paths and combinatorial behaviour nobody understands.
Flag Evaluation Latency	concept	Client Feature Flags	The delay between page load and the client knowing which variant to show, which produces a visible flicker unless the flag is resolved before render.
Flake Rate Test Nondeterminism, Suite Trust Threshold, Intermittent Failure Rate	concept	Flaky Test Management	The proportion of test failures that are not caused by a real defect - a quantity with a sharp threshold, above which the suite stops being a signal and starts training the team to ignore failures.
Flaky Test	concept	Flaky Test Management	A test that passes and fails on unchanged code, destroying the signal value of the entire suite it belongs to.
Fleet Reconnection Storm Device Thundering Herd, Synchronised Reconnect, IoT Recovery Surge	concept	Device Telemetry at Scale	A synchronised burst of devices re-establishing connections after any disruption, which is far more expensive than steady-state traffic and routinely turns a brief platform blip into a prolonged outage.
Fleet-Wide Change Reach Platform Change Propagation	concept	Service Templates	How long it takes a platform change to reach the majority of the services built on it - the measure of whether a platform can actually change anything.
Flow Efficiency Work-to-Wait Ratio, Process Cycle Efficiency	concept	Value Streams	The proportion of elapsed lead time in which work is actively being done - typically very low, which is why optimising engineering throughput addresses the minority of the problem.
Foreign Key Constraint	concept	Relational Modelling	A database-enforced rule that a referencing value must exist in the referenced table — referential integrity that no application bug can violate.
Fork-Triggered Build Privileged Trigger, Pwn Request	concept	Pipeline Secrets	A continuous-integration trigger that runs a workflow in the base repository's privileged context while its inputs come from an outside contributor - so the pipeline executes attacker-authored code with its ow…
Fourth Party Risk	concept	Third-Party Risk	The dependencies of your dependencies, which you did not choose, may not know about, and remain accountable for.
Fragmentation Cost Bin-Packing Loss, Scheduling Fragmentation	concept	Compute Models	The capacity that exists in aggregate but cannot be used because it is scattered across nodes in pieces too small for the jobs that need it - the dominant inefficiency in indivisible-resource scheduling.
Freshness Requirement	concept	Streaming vs Batch	How stale data may be before the decision it supports degrades — the only question that justifies streaming over batch.
Friction Budget	concept	Security vs Usability	The limited amount of security friction users will absorb before they work around it, making usability a security property rather than its opponent.
Frontend Architecture	concept	Frontend & Experience Architecture	The structural decisions in client applications — rendering strategy, state ownership, boundaries and delivery — which have the same character as backend ones and are frequently made by default.
Frontend Security Boundary	concept	Frontend Security	The rule that nothing enforced in the browser is a security control, and the browser-side mechanisms that reduce blast radius anyway.
Fully-Loaded Tenant Cost True Cost to Serve, Cost Per Tenant, Loaded Unit Cost	concept	Unit Economics	The total cost of serving one tenant including the per-tenant floors that do not scale with usage - infrastructure minimums, control-plane overhead, fleet operations, support and abuse - which is what makes sm…
Functional Cohesion	concept	Cohesion	The strongest form of cohesion, in which every element of a module contributes to a single well-defined task.
Functional Equivalence Switching Equivalence, Same-Service-Type Equivalence	concept	Sector Cloud Rules	The standard that a destination service must deliver the same output at the same performance and security after a switch, which is defined only between services of the same type and therefore does not rescue a…
Functional vs Non-Functional Behaviour vs Quality of Behaviour	concept	Functional vs Non-Functional	Functional requirements say what the system does; non-functional requirements say how well, and only the second constrains structure.
Fundable Boundary Budget-Aligned Boundary, Ownable Boundary	concept	Operating Models	A service boundary that sits inside one budget line and one approver - the condition under which it survives contact with the organisation rather than being re-crossed by the first urgent change.
Gang Scheduling Co-scheduling, All-or-Nothing Allocation	concept	Compute Models	Allocating every resource a job needs simultaneously or not at all, so tightly-coupled distributed work cannot deadlock holding a partial allocation.
Gateway Timeout Chain	concept	API Gateways	The sequence of timeouts from client through load balancer, gateway and service, which must decrease inward or produce confusing failures.
Geo-Blocking Accuracy	concept	Geo-Restriction & Sanctions	The reliability of determining a user's jurisdiction from network signals, which is imperfect in both directions and therefore needs a designed handling of errors.
Golden Record	concept	Master Data Management	The single authoritative version of an entity assembled from conflicting sources, and the survivorship rules that decide which value wins.