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

46 terms shown.

Term	Kind	Topic	What it is
Ambiguous Outcome Unknown State, Indeterminate Result	concept	Timeouts & Deadlines	The state a system is in when a call times out - not failure, but unknown - and the design obligation to have somewhere to put it.
Atomic Commit Protocol	concept	Distributed Transactions	Any protocol ensuring that several participants reach the same decision to commit or abort — and a problem provably unsolvable with certainty in an asynchronous system with failures.
Backpressure	concept	Distributed Systems	A mechanism by which a component under load tells its callers to slow down, rather than accepting work it cannot complete.
Byzantine Fault	concept	Failure Modes	A failure in which a component behaves arbitrarily or deceptively — returning wrong results rather than stopping — as distinct from simply crashing.
CAP Theorem Brewer's Theorem	concept	Distributed Systems	During a network partition a distributed system must choose between consistency and availability; it cannot have both.
Cascading Timeout	concept	Timeouts & Deadlines	The effect of independently-chosen per-hop timeouts summing to a total far longer than any caller is willing to wait.
Causal Consistency	concept	Consistency Models	A model guaranteeing that operations which causally depend on one another are seen in the same order everywhere, while concurrent operations may be seen in any order.
Circular Observability Dependency Blind Spot Cycle, Self-Observing Stack, Telemetry Co-Failure	concept	Failure Modes	When the tooling used to diagnose a failure runs on the infrastructure that is failing - so the outage removes the ability to see the outage, converting a technical problem into a search problem.
Clocks and Ordering Logical Clocks, Happens-Before	concept	Clocks & Ordering	Why wall-clock timestamps cannot order events across machines, and the mechanisms that can.
Compensation Impossibility Irreversible Step, Uncompensatable Action	concept	Sagas & Compensation	The recognition that some saga steps have no true compensating action, and the design rule that follows - order steps by reversibility and gate the irreversible ones.
Consistent Prefix Read	concept	Consistency Models	A guarantee that if a sequence of writes happens in a given order, a reader sees a prefix of that sequence — never an out-of-order subset.
Consumer Group	concept	Event Streaming	A set of consumers that cooperatively read one stream, with each partition assigned to exactly one member, so the group collectively processes every message once.
Control-Interval Matching Actuation Delay Matching, Feedback Loop Damping	concept	Failure Modes	Setting a feedback loop's control interval to the delay of the thing it actuates - because a controller that adjusts faster than the system can respond amplifies noise instead of correcting error.
Deadline Exceeded	concept	Timeouts & Deadlines	The error returned when a request's overall budget expires — semantically distinct from a per-hop timeout, and a signal that must not be retried blindly.
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.
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.
Fan-Out	concept	Distributed Systems	One incoming request causing many outgoing ones, which multiplies both load and tail latency.
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 Tolerance	concept	Distributed Systems	Continuing to operate correctly despite the failure of some components, by design rather than by luck.
Gray Failure Partial Failure, Fail-Slow	concept	Failure Modes	A component that is degraded rather than down, passing health checks while serving a portion of requests slowly or incorrectly.
Grey Failure Partial Failure, Fail-Slow	concept	Failure Modes	A component that is degraded rather than down — slow, intermittently erroring, or failing for a subset of operations — which defeats health checks built for binary states.
Half-Open State	concept	Circuit Breakers	The circuit breaker state that allows a limited number of trial requests through to test whether a failed dependency has recovered.
Harvest and Yield	concept	CAP & PACELC	A refinement of CAP that treats availability as a continuum — yield is the fraction of requests answered, harvest is the fraction of data reflected in an answer.
Idempotency	concept	Distributed Systems	The property that performing an operation many times has the same effect as performing it once.
Invariant-Aligned Partitioning Partition by Invariant, Single-Writer Per Entity	concept	Consistency Models	Choosing the partition key so that every strong-consistency invariant falls entirely inside one partition - which converts distributed coordination into local serialisation.
Jitter	concept	Retries & Backoff	Randomising retry delays so that clients that failed together do not retry together.
Lease	concept	Distributed Locking	A lock with an expiry, granting exclusive rights for a bounded time so that a crashed holder cannot block the system forever.
Linearizability Atomic Consistency, Strong Consistency	concept	Consistency Models	The strongest single-object guarantee — every operation appears to take effect instantaneously at some point between its call and its return.
Lock Lease Expiry	concept	Distributed Locking	The timeout on a distributed lock that prevents a crashed holder deadlocking the system — and the source of the pattern's hardest failure mode.
Message Ordering	concept	Messaging & Queues	The guarantee about the sequence in which messages are delivered — normally per-partition or per-group only, and lost the moment consumption is parallelised.
Metastable Failure Congestive Collapse, Death Spiral	concept	Failure Modes	A failure state that sustains itself after the original trigger is gone, because the system's own recovery behaviour generates the load keeping it down.
Offset Management	concept	Event Streaming	How a consumer records its position in a stream, and the decision that determines whether processing is at-least-once or at-most-once.
PACELC	concept	CAP & PACELC	An extension of CAP stating that during a partition you trade availability against consistency, and else — in normal operation — you trade latency against consistency.
Partition Tolerance	concept	CAP & PACELC	The ability to keep operating when the network drops or delays messages between nodes — not a choice, but a property of any system spanning more than one machine.
Pivot Transaction	concept	Sagas & Compensation	The step in a saga after which the transaction can no longer be cancelled — everything before it is compensatable, everything after it is retriable until it succeeds.
Quorum	concept	Consensus Protocols	The minimum number of replicas that must respond for an operation to be considered committed, sized so that any read set and any write set must overlap.
Read Timeout Socket Timeout	concept	Timeouts & Deadlines	The bound on how long a client waits for response data after a connection is established — distinct from the connect timeout, and the one that usually matters.
Read-Your-Writes Consistency Read-After-Write	concept	Consistency Models	A guarantee that a client always sees its own prior writes, even in a system that is otherwise eventually consistent.
Reconnect Storm Connection Stampede	concept	Distributed Systems	The synchronised reconnection of a large population of clients after a disruption, which routinely causes a larger outage than the disruption itself.
Scalability	concept	Distributed Systems	The ability to handle growing load by adding resources, ideally with cost rising no faster than the load.
Service Discovery	concept	Distributed Systems	The mechanism by which a caller finds a currently healthy network address for a service whose instances are ephemeral.
Split Brain	concept	Leader Election	A partition in which two subsets of a cluster each believe they are authoritative, accepting conflicting writes that cannot afterwards be reconciled.
Split Vote	concept	Leader Election	An election in which no candidate obtains a majority, so the term ends with no leader and the process must repeat.
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.
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.