Terminology

2185 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 areas2185 Architecture Fundamentals77 Distributed Systems107 Data Architecture110 Cloud Architecture89 Networking88 API & Integration Architecture82 Reliability & Resilience75 Observability70 Performance & Capacity Engineering72 Security Architecture81 Cost Architecture & FinOps66 Business Architecture67 Architecture Communication67 Enterprise Architecture66 Legacy Modernization66 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 concept785 practice729 pattern362 metric125 case-study77 tool62 protocol45

72 terms shown.

Term	Kind	Topic	What it is
Access Pattern Skew Popularity Skew, Zipf Distribution	concept	Caching for Performance	The uneven distribution of requests across keys - which determines whether caching helps at all, and which synthetic load tests systematically fail to reproduce.
Adaptive Admission Level Priority Admission Threshold, Collaborative Load Shedding	pattern	Queueing Theory	A load-dependent priority threshold that a service publishes back to its callers, so requests that would be rejected downstream are never sent and upstream work is not wasted.
Admission Queue Virtual Waiting Room, Login Queue, Front-Door Queue	pattern	Performance & Capacity	Holding excess arrivals in an explicit, communicated queue and admitting them at a rate the system can serve - converting an overload failure into a wait, which is a far better outcome and must be built in advance.
Amdahl's Law	concept	Profiling & Optimisation	The limit on speedup from optimising or parallelising part of a system, set by the proportion of work that remains unchanged.
Bottleneck	concept	Bottleneck Analysis	The single resource that limits system throughput, such that improving anything else produces no gain.
Bottleneck Analysis	practice	Bottleneck Analysis	Finding the single resource that limits the system, because improving anything else changes nothing.
Breaking-Point Testing Test to Failure, Constraint Discovery	practice	Load Testing	Pushing a load test past the target until the system fails, because the purpose of a load test is to locate the constraint and the failure mode rather than to confirm a number.
Cache Hit Ratio Economics	concept	Caching for Performance	The non-linear relationship between cache hit rate and backend load, which determines whether a cache improvement is worth making.
Cache Stampede Thundering Herd, Dog-Piling	concept	Caching for Performance	The surge of identical expensive requests to the origin when a popular cache entry expires and many concurrent callers all miss at once.
Caching Strategy	pattern	Performance & Capacity	The chosen pattern for how a cache is populated, read and invalidated — cache-aside, read-through, write-through or write-behind.
Capacity Lead Time Provisioning Lead Time	concept	Capacity Modelling	The delay between deciding capacity is needed and having it available, which determines whether a capacity model can forecast at all or must instead buy optionality.
Capacity Modelling	practice	Capacity Modelling	Predicting the resources a workload will need, from measured unit costs and a demand forecast, with deliberate headroom.
Collective Communication Cost Allreduce Overhead, Synchronisation Cost at Scale	concept	Throughput	The synchronisation term that determines how far a distributed training or inference job can scale, made of a bandwidth component that is nearly flat in participant count and a latency component that is not.
Concurrency	concept	Concurrency	How many operations are in flight at once — the quantity that actually saturates a system, and the one most worth limiting explicitly.
Connection Pool	concept	Performance & Capacity	A fixed set of reusable database connections shared by an application's requests, and one of the most common hidden capacity ceilings.
Connection Pool Sizing	practice	Connection Pooling	Choosing how many concurrent connections a service holds to a datastore, where both too many and too few cause outages.
Coordinated Omission Closed-Loop Measurement Bias, Omitted Latency Samples	concept	Load Testing	The measurement error in which a load generator stops issuing requests while the system under test is stalled, so the slow samples that a real arrival process would have produced are never recorded.
Database Performance	practice	Database Performance	The interventions that resolve database bottlenecks, in the order they should be attempted.
Deadline-Derived Queue Depth Deadline-Bounded Queue	concept	Concurrency	The rule that a request queue's maximum depth comes from the client's deadline and the service's completion rate, so the queue can never hold work that will expire before it is served.
Demand Forecasting	practice	Capacity Modelling	Projecting future load from historical trends, business plans and known events, and translating it into resource requirements with explicit lead times.
Efficient Concurrency Point Optimal Pool Size, Contention Threshold	concept	Connection Pooling	The concurrency level beyond which adding parallel work reduces total throughput, because contention costs more than the parallelism gains - and the reason a larger connection pool often makes latency worse.
Ephemeral Port Exhaustion Source Port Starvation, TIME_WAIT Exhaustion	concept	Network Performance Tuning	The failure in which a host runs out of source ports for new connections to one destination, producing connection errors that look like the remote being down while the remote is healthy.
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.
Flame Graph	tool	Profiling & Optimisation	A visualisation of sampled stack traces in which width represents time spent, used to identify where a program's execution actually goes.
Goodput Useful Throughput	metric	Throughput	The rate of completed work that someone is still waiting for, which diverges from throughput under overload and is the only rate that tracks what users receive.
Google Maps and Planetary-Scale Spatial Serving	case-study	Performance & Capacity	Map serving is fast because almost nothing is computed on request — the world is precomputed into a pyramid of tiles, and space is indexed onto a one-dimensional curve.
Horizontal vs Vertical Scaling Scale Out vs Scale Up	concept	Performance & Capacity	Adding more machines versus making one machine bigger — and the fact that vertical is underrated for stateful tiers.
In-Memory Reservation Service Inventory Reservation Service, Single-Owner Counter, Memory-Speed Allocation	pattern	Database Performance	Moving a heavily-contended counter or inventory pool into a single-owner in-memory service that serialises decisions at memory speed and persists asynchronously, trading a small durability window for orders of…
Index Write Amplification Index Maintenance Cost, Secondary Index Overhead	concept	Database Performance	The multiplication of write work caused by secondary indexes, where every insert and every update to an indexed column must also maintain each index tree inside the same transaction.
Latency	metric	Latency	How long one operation takes — a distribution, never a number, and dominated by its tail in any system with fan-out.
Latency Budget Decomposition	practice	Latency	Allocating a total response-time target across the components of a request path, so each layer has an explicit share and overruns are attributable.
Little's Law	concept	Performance & Capacity	In a stable system, the average number of items in it equals the arrival rate times the average time each spends in it — L = λW.
Little's Law Applied to Pools	practice	Connection Pooling	Using L = λW to size connection and thread pools from measured throughput and latency rather than from a default.
Little's Law in Practice	metric	Little's Law	L = λW — concurrency equals arrival rate times latency — and the reason a slowdown becomes an outage.
Load Testing	practice	Performance & Capacity	Driving a system with realistic traffic at a target volume to verify it meets its performance targets before real users do.
Load Testing in Practice	practice	Load Testing	Verifying behaviour under expected load — where realism of workload and data matters more than the number of virtual users.
Network Performance Tuning	practice	Network Performance Tuning	The application-level and connection-level changes that actually improve networked performance, in order of effect.
Overload Recovery Time Overload Settling Time	metric	Stress Testing	Wall-clock time from the moment load returns to normal until the system is fully healthy again, which is set by spare capacity rather than by service speed.
Parallelism and Concurrency	concept	Concurrency	The distinction between structuring work so it can make progress independently and actually executing work simultaneously on multiple cores.
Payload Compression Trade-off	concept	Network Performance Tuning	The exchange of CPU time for reduced transfer time, which is favourable on constrained networks and harmful on fast local ones.
Peak Event Readiness	practice	Peak Event Readiness	Preparing for a known, dated, high-stakes traffic event — where the discipline is as much organisational as technical.
Peak Readiness Rehearsal Pre-Event Verification, Scheduled Peak Drill	practice	Peak Event Readiness	The set of pre-peak actions and verifications - warm caches, warm pools, confirmed dependency headroom, a change freeze, a rehearsed shedding path - without which correct capacity still fails.
Percentile Latency	metric	Latency	Latency expressed as the value below which a given proportion of requests fall, used because averages conceal the behaviour that users notice.
Performance Budget	practice	Performance Budgets	A stated numeric limit on a performance characteristic, enforced automatically so that regressions fail a build rather than accumulating.
Performance Budget for Backends	practice	Performance Budgets	A latency or resource allowance allocated per component of a request path, so that the end-to-end target is composed rather than hoped for.
Pre-Scaling Scheduled Scaling, Warm Provisioning, Capacity Staging	practice	Peak Event Readiness	Provisioning capacity in advance of a known event rather than relying on autoscaling, because the arrival spike at a scheduled moment is faster than any reactive control loop can respond to.
Profiling and Optimisation	practice	Profiling & Optimisation	The discipline of measuring before changing, optimising the dominant term, and stopping when the objective is met.
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.
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.
Queueing Delay	concept	Queueing Theory	The time a request spends waiting rather than being served, which rises non-linearly as utilisation approaches capacity.
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.
Retail Peak: Designing for Black Friday Black Friday Readiness	case-study	Peak Event Readiness	A retailer's annual peak can be an order of magnitude above normal, arrives in minutes, and cannot be rescheduled — which makes it a distinct engineering discipline.
Saturation Point	concept	Throughput	The load level beyond which additional demand produces queueing and latency growth rather than additional completed work.
Scale Cube	concept	Horizontal vs Vertical Scaling	A model describing three independent axes of scaling — cloning, functional decomposition, and data partitioning — each addressing a different limit.
Segment-Isolated Serving Outlier Tenant Path, Heavy-User Isolation	pattern	Tail Latency	Giving a consistently slow population its own path - pool, precomputed view, or query strategy - rather than optimising the shared path to accommodate it.
Soak Test	practice	Soak Testing	Running sustained realistic load for hours or days to expose defects that accumulate over time rather than appearing under peak load.
Soak Testing	practice	Soak Testing	Running at sustained realistic load for hours or days to find the failures that only appear with time.
Stress Test	practice	Stress Testing	Driving load beyond expected capacity to observe how the system behaves at and past its breaking point.
Stress Testing	practice	Stress Testing	Deliberately exceeding capacity to find where the system breaks and — more importantly — how.
Tail Composition Effect Fan-Out Tail Amplification, Page-Level Tail	concept	Tail Latency	The multiplication that turns a small per-request slow rate into a large user-visible slow rate, because a single user action makes many requests and is only as fast as its slowest one.