Terminology

991 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 areas991 Architecture Fundamentals38 Distributed Systems73 Data Architecture71 Cloud Architecture55 Networking51 API & Integration Architecture45 Reliability & Resilience40 Observability33 Performance & Capacity Engineering34 Security Architecture50 Cost Architecture & FinOps30 Business Architecture28 Architecture Communication27 Enterprise Architecture27 Legacy Modernization27 AI-Era Architecture34 Software Architecture & Engineering37 Architecture Patterns34 Architecture Decision-Making30 The Architect's Meta-Skills27 Delivery & Release Engineering20 Platform Engineering & Developer Experience20 Testing & Quality Architecture20 Data Platform Architecture20 Streaming & Real-Time Data20 Data Governance & Semantics20 Frontend & Experience Architecture20 Edge, Mobile & IoT20 Regulatory & Data Protection Architecture20 Assurance, Audit & Model Risk20

Kind Any concept379 practice294 pattern166 metric55 tool36 protocol35 case-study26

20 terms shown.

Term	Kind	Topic	What it is
Changelog Stream	concept	Stream-Table Duality	A stream whose records are keyed updates, so replaying it from the beginning reconstructs a table — the same information in the other of its two forms.
Checkpoint Interval	metric	Stream Processing Frameworks	How often a stateful processor persists its state and offsets, which trades steady-state overhead against how much work is redone after a failure.
Consumer Lag	metric	Streaming SLOs	How far behind the newest record a consumer is, expressed in time rather than in message count, and its rate of change.
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.
Feature Staleness	metric	Feature Freshness	The age of the feature values a model scores against, and the divergence between how they are computed at training time and at inference time.
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.
Idempotent Sink	pattern	Exactly-Once Semantics	A destination where writing the same record twice has the same effect as writing it once, which is what makes end-to-end exactly-once achievable at all.
Key Skew	concept	Partition Keys & Ordering	An uneven distribution of records across partitions, which caps throughput at the busiest partition regardless of how many exist.
Keyed State Size	metric	Stateful Stream Processing	The total state a job holds per key across all keys, which governs memory, checkpoint duration and recovery time.
Poison Message	concept	Dead Letter Handling	A record that a consumer cannot process and cannot skip, which halts its partition entirely until someone intervenes.
Replay Pipeline	pattern	Kappa vs Lambda	A single processing path that produces both live and historical results by re-running the same code over retained input, replacing the two-path Lambda arrangement.
Reprocessing Window	concept	Backfill & Reprocessing	How far back a pipeline can be replayed, set by the shortest retention anywhere along the path rather than by intent.
Retention Cost	metric	Streaming Cost	The storage bill for keeping a log replayable, which is set by retention multiplied by throughput multiplied by the replication factor.
Schema Compatibility Mode	concept	Streaming Schema Evolution	The rule stating which schema changes a registry will accept, which encodes whether producers or consumers are expected to upgrade first.
Serving Latency Budget	concept	Real-Time Serving Layer	The end-to-end time from an event occurring to its effect being queryable, allocated across ingest, processing and serving.
Stream Enrichment	pattern	Streaming Joins	Attaching reference data to a stream by lookup against a materialised table rather than by joining two unbounded streams.
Sub-Second Aggregation Store	tool	Real-Time Analytical Stores	A database built to ingest continuously and answer aggregate queries over recent data in milliseconds, occupying the gap between OLTP and the warehouse.
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.
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.
Watermark Lag	metric	Watermarks & Late Data	How far behind the newest event a watermark is held, which trades result latency against how much late data is included.