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
Tail Latency p99, p999	metric	Performance & Capacity	The latency experienced by the slowest small percentage of requests, which is what users and dependent services actually feel.
Tail Latency Amplification Fan-out Tail, Slowest-Component Latency	concept	Tail Latency	A parallel fan-out completes when its slowest component does, so ordinary per-component tails combine into a much worse end-to-end tail.
Tail Latency Amplification	concept	Tail Latency	The effect where a request that fans out to many services experiences the worst case of all of them, making rare slowness common at the user level.
Throughput	metric	Throughput	Work completed per unit time — bounded by the system's narrowest resource, and traded against latency.
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.
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.
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 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.
WhatsApp's Small-Team Scale	case-study	Performance & Capacity	WhatsApp served hundreds of millions of users with a few dozen engineers by matching one technology choice precisely to the workload and refusing to add anything else.
Working Set Hot Data Set	concept	Caching for Performance	The subset of data actually touched in a given window, whose size against the cache's capacity determines the hit rate and therefore how much load reaches the origin.
Workload Model	practice	Load Testing	A description of the traffic mix, arrival pattern and data distribution a load test reproduces, which determines whether the test's results mean anything.
Write Contention Row Contention, Hot Row	concept	Performance & Capacity	Many concurrent writers competing for the same item of state, which serialises through one lock and cannot be relieved by adding capacity.