Terminology

454 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 areas454 Architecture Fundamentals16 Distributed Systems73 Data Architecture71 Cloud Architecture55 Networking13 API & Integration Architecture17 Reliability & Resilience16 Observability14 Performance & Capacity Engineering13 Security Architecture50 Cost Architecture & FinOps12 Business Architecture9 Architecture Communication8 Enterprise Architecture8 Legacy Modernization11 AI-Era Architecture15 Software Architecture & Engineering19 Architecture Patterns15 Architecture Decision-Making11 The Architect's Meta-Skills8

Kind Any concept166 practice107 pattern93 case-study26 tool26 protocol22 metric14

166 terms shown.

Term	Kind	Topic	What it is
Embedding	concept	AI-Era Architecture	A dense numeric vector representing a piece of content, positioned so that semantically similar content sits nearby.
Encapsulation	concept	Architecture Fundamentals	Keeping a component's state private, so it can only be changed through operations that maintain its invariants.
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.
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.
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.
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.
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.
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.
Hot Partition Hot Shard, Hot Key	concept	Partitioning & Sharding	One partition receiving disproportionate traffic, so the system saturates at a fraction of its aggregate capacity.
Hot, Warm and Cold Data	concept	Data Lifecycle & Retention	Classifying data by how frequently and how urgently it is accessed, so each tier can be stored on media priced for that access pattern.
Idempotency	concept	Distributed Systems	The property that performing an operation many times has the same effect as performing it once.
Identity and Access Management IAM	concept	Security Architecture	The system of record for principals, credentials and permissions, and the policy engine that decides what each principal may do.
Instance Family	concept	Compute Models	A group of instance types sharing a resource profile — general purpose, compute optimised, memory optimised, storage optimised, accelerated — chosen by which resource the workload actually exhausts first.
Join Strategies	concept	Query Optimisation	The three ways a database combines two row sets — nested loop, hash join and merge join — and the conditions under which each is correct.
Layer 4 vs Layer 7 Load Balancing	concept	Networking	Balancing on connection metadata (IP and port) versus on the content of the request (path, host, headers).
Lease	concept	Leader Election	Time-bounded leadership or ownership that must be renewed before it expires, so a leader that becomes unreachable automatically relinquishes its role.
Least Privilege	concept	Security Architecture	Granting each identity only the permissions it needs, for only as long as it needs them.
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.
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.
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.
Log Compaction	concept	Event Streaming	A retention policy that keeps only the most recent value for each key rather than deleting by age, so the log becomes a durable snapshot of current state.
Managed Service	concept	Cloud Architecture	A capability the provider operates — provisioning, patching, backup, scaling and failover — leaving you the configuration and the data.
Managed Service Upgrade Window	concept	Managed Services	The period during which a provider may apply patches or version upgrades to a managed service, usually involving a failover or brief unavailability.
Managed vs Self-Managed	concept	Architecture Decision-Making	Trading control, portability and unit cost against the operational burden of running the thing yourself.
Mass Assignment Auto-Binding, Over-Posting	concept	Secure API Design	A vulnerability where a request body is bound directly to an internal object, allowing a caller to set fields the API never intended to expose.
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.
Modularity	concept	Architecture Fundamentals	The degree to which a system is composed of parts that can be understood, changed and replaced independently.
Monolith vs Microservices	concept	Architecture Decision-Making	A trade of deployment independence against distributed-systems complexity, decided by team topology far more often than by technology.
Multi-Cloud	concept	Cloud Architecture	Deliberately running across more than one cloud provider — a decision with a much higher cost than the lock-in it is usually adopted to avoid.
Noisy Neighbour	concept	Bulkheads & Isolation	One tenant or workload consuming shared resources to the detriment of others sharing the same infrastructure.
Non-Functional Requirement NFR, Quality Attribute	concept	Architecture Fundamentals	A requirement about how well the system must behave rather than what it must do — latency, availability, throughput, security, cost.
Object Storage	concept	Cloud Architecture	Flat, HTTP-addressable storage for immutable blobs with rich metadata — effectively unlimited, cheap, and not a filesystem.
Object-Level Authorization BOLA, IDOR	concept	Authorization	Checking that the caller is entitled to the specific record they requested, not merely that they may call the endpoint.
Observability	concept	Observability	The property of being able to answer new questions about a system's internal state from its external outputs, without shipping new code.
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.
OLTP vs OLAP	concept	Data Warehousing	Two workload shapes with opposite requirements — many small indexed transactions versus few large scans and aggregations — which is why they belong in different stores.
Operational vs Analytical Store	concept	Polyglot Persistence	The separation between the store serving the application's transactions and the one serving reporting and analysis, and the mechanism connecting them.
PACELC	concept	CAP & PACELC	An extension of CAP that also describes the normal case — if Partitioned choose Availability or Consistency, Else choose Latency or Consistency.
Partial Index Filtered Index	concept	Indexing	An index built over only the rows matching a predicate, so it is far smaller and cheaper to maintain than a full index.
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.
Permission Boundary	concept	Identity & Access Management	A policy limiting the maximum permissions an identity can have, used so that the ability to create roles does not become the ability to grant unlimited privilege.
Personally Identifiable Information PII, Personal Data	concept	Security Architecture	Data relating to an identifiable person — a category far broader than name and address, and the trigger for most regulatory obligation.
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.
Pod	concept	Kubernetes	The smallest deployable unit in Kubernetes — one or more containers that share a network namespace, storage volumes and a lifecycle, scheduled together on one node.
Point-in-Time Recovery PITR	concept	Backup Strategies	Restoring a database to any moment within a retention window by replaying transaction logs onto a base backup, rather than only to a snapshot boundary.
Prompt Injection	concept	AI-Era Architecture	An attack in which text from an untrusted source is interpreted by the model as instructions rather than as data.
Provisioned vs Serverless Capacity	concept	Cloud Databases	Paying for a fixed database size continuously, versus paying for capacity consumed with automatic scaling — a crossover decision driven by duty cycle.
Purpose Limitation	concept	Privacy Engineering	The principle that personal data collected for one stated purpose may not be used for an unrelated one without a new lawful basis.
Query Plan Execution Plan, EXPLAIN	concept	Data Architecture	The database's chosen strategy for executing a query, and the first thing to look at when one is slow.
Quorum	concept	Distributed Systems	A minimum number of nodes that must acknowledge an operation for it to count, chosen so that read and write sets are guaranteed to overlap.
Re-architect vs Rebuild	concept	Legacy Modernization	Restructuring an existing system incrementally versus writing a replacement from scratch — and the strong evidence that incremental wins.
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 session guarantee that a client always sees its own updates, even when reads are served from replicas that may lag.
Redundancy	concept	Reliability & Resilience	Having more instances of a component than the load requires, so that failures can be absorbed without loss of service.