Terminology

2205 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 areas2205 Architecture Fundamentals77 Distributed Systems107 Data Architecture110 Cloud Architecture94 Networking88 API & Integration Architecture82 Reliability & Resilience75 Observability70 Performance & Capacity Engineering72 Security Architecture86 Cost Architecture & FinOps71 Business Architecture67 Architecture Communication67 Enterprise Architecture66 Legacy Modernization71 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 concept794 practice734 pattern368 metric125 case-study77 tool62 protocol45

794 terms shown.

Term	Kind	Topic	What it is
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.
Observability Cost	concept	Observability Cost	Monitoring spend that grows with traffic and frequently reaches a meaningful fraction of infrastructure cost — controlled by sampling, cardinality and retention.
Observable Component Contract Rendered Surface Contract, Implicit Component API	concept	Component Contracts	The full set of things a consumer can depend on in a shared component - DOM structure, class names, computed spacing, specificity and render timing - as distinct from its declared props, which is the only part…
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.
One-Way Door Irreversible Decision, Type 1 Decision, Foreclosed Option	concept	Reversibility	A decision whose reversal is prohibitively expensive or impossible, which is where analytical effort belongs - as distinct from the reversible majority, where deliberation typically costs more than being wrong.
One-Way Door Decision Type 1 Decision, Irreversible Decision	concept	Reversibility	A decision that is very costly or impossible to reverse, warranting deliberation proportionate to that permanence.
Operated Reliability Realised Availability	concept	Reliability vs Complexity	The availability a system actually achieves in the hands of the team running it - as distinct from the availability its topology implies.
Operating Effectiveness	concept	Control Design vs Operation	Whether a control actually ran, consistently, over a period — as distinct from whether it was well designed, and the harder of the two to demonstrate.
Operating Model	concept	Operating Models	How an organisation arranges people, process, technology and governance to deliver its capabilities, which constrains architecture as strongly as any technical factor.
Operating Models	concept	Operating Models	How an organisation arranges people, ownership and decision rights to deliver and run systems — which determines what architectures are viable.
Operational Resilience Requirement	concept	Financial Services Regulation	A supervisory expectation that a firm can continue delivering critical business services through disruption, expressed as an impact tolerance it must evidence.
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.
Operator Independence	concept	Digital Sovereignty	The requirement that no foreign entity can be compelled to access or disclose data, which goes beyond where the bytes are stored to who controls the operator.
Organisational Constraints	concept	Organisational Constraints	The structural, procedural and human limits that determine which designs can actually be built and operated here.
Organisational Readiness	concept	Organisational Constraints	Whether an organisation has the skills, capacity, structure and appetite to operate a proposed architecture, independent of the design's technical merit.
Orphaned Resource	concept	Waste Elimination	Infrastructure that is billed but serves nothing, typically left behind when the thing it supported was deleted.
Outcome over Output	concept	Product Thinking	Measuring and committing to changes in user or business behaviour rather than to the delivery of features.
Over-Classification Label Inflation, Maximum Propagation Collapse	concept	Sensitivity Labelling	The state in which so much of an estate carries the highest sensitivity label that its controls become unworkable, and people route around them - producing less protection than a coarser scheme would.
Over-Engineering	concept	Pragmatism	Building capability the requirements do not justify, paying its complexity cost continuously in exchange for flexibility that is rarely used.
Over-Fetching	concept	API Shapes for UI	Transferring fields the interface will not display, which costs bandwidth and parse time on exactly the devices least able to afford them.
OWASP Risks OWASP Top Ten	concept	OWASP Risks	The recurring application vulnerability classes — and the architectural decisions that make each one structurally unlikely.
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.
Parallelism and Concurrency	concept	Concurrency	The distinction between structuring work so it can make progress independently and actually executing work simultaneously on multiple cores.
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 Assignment	concept	Competing Consumers	The mapping of partitions to consumer instances that determines parallelism, ordering guarantees and what happens when the consumer set changes.
Partition Count Immutability Fixed Partition Count, Key-to-Partition Remap Hazard	concept	Partition Keys & Ordering	The partition count of a keyed log is effectively permanent, because raising it changes which partition a key hashes to and therefore breaks per-key ordering and every table rebuilt by replaying that log.
Partition Key Skew Hot Partition, Key Skew	concept	Partition Keys & Ordering	One partition receiving disproportionate traffic because a small number of key values dominate, capping throughput at what a single consumer can handle.
Partition Pruning	concept	Storage Layout & Partitioning	The query engine skipping entire partitions whose values cannot match the filter, which is where most large-table query performance comes from.
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.
Partitioning and Sharding	concept	Partitioning & Sharding	Splitting data by a key — within one database for manageability, or across databases for capacity and isolation.
Pass-Through Cost of Goods Sold Third-Party Unit Cost, Supplier Pass-Through Term	concept	Cost per Request	The part of the cost of serving one unit that is paid to a third party per transaction, which infrastructure optimisation cannot reduce and which eventually decides whether unit cost keeps falling.
Path MTU Discovery PMTUD	concept	Network Troubleshooting	The mechanism by which a sender discovers the largest packet size a path supports, and a common cause of connections that establish and then hang.
Path MTU Discovery Failure MTU Black Hole, PMTUD Blackhole	concept	Network Troubleshooting	Large packets silently discarded because the ICMP messages that would report the size limit are blocked - producing the signature "small requests work, large transfers hang".
Pattern Overuse	concept	Design Patterns	Applying a design pattern where the problem it solves does not exist, adding indirection and vocabulary without benefit.
Pattern Scope Discipline Apply the Pattern to a Use Case, Not the System	concept	CQRS	The rule that heavyweight data patterns - CQRS, event sourcing, materialised read models - belong to the specific part of a domain that needs them, never to a whole product.
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.
Performance versus Cost	concept	Performance vs Cost	The trade between latency and spend — where headroom is the mechanism and high utilisation is the false economy.
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.
Physical World Failure Mode	concept	Physical-World Failure Modes	The failure classes that only exist once software controls or observes physical equipment, where the system cannot be restarted and the consequences are not confined to data.
Pipeline Stage Contract	concept	Delivery & Release Engineering	What each pipeline stage promises the next — an artifact of a stated shape plus a specific claim about it that has been verified.
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.
Platform Abstraction Level	concept	Abstraction Level Choice	How far a platform hides the underlying infrastructure, and the leak-versus-flexibility trade it makes at that height.
Platform API	concept	Platform APIs	The programmatic contract through which teams consume platform capabilities, and the thing that must stay stable while everything behind it changes.
Platform Bypass Signal Adoption as Feedback, Voluntary Platform Use	concept	Platform as a Product	Teams routing around an internal platform read as a product signal about the platform's fitness, not as a compliance failure to be solved with a mandate.
Platform Contract	concept	Platform APIs	The platform's promise to its consumers about interface stability, behaviour and support, treated with the same seriousness as an external API.
Platform Engineering	concept	Platform Engineering	Building internal products that reduce the cognitive load on delivery teams — with self-service as the property that separates it from a service desk.
Platform Funding Model	concept	Platform Funding	How internal platform work is paid for, which determines what the platform optimises for and whether it survives a budget cycle.
Platform Lifecycle Constraint	concept	Mobile App Architecture	The operating system's rules about when your process runs, which are not negotiable and invalidate most assumptions carried over from server code.
Platform Teams	concept	Platform Teams	Teams providing self-service internal capability to reduce the cognitive load on delivery teams — distinguished from a service desk by self-service.
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 Correctness As-Of Join, Temporal Correctness, Leakage Prevention	concept	Semantic Layer	Retrieving each feature's value as it was at the moment of the event rather than its current value, which is what prevents a model from training on information that did not exist yet.
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.
Poison Message	concept	Dead Letter Handling	A record that a consumer cannot process and cannot skip, which halts its partition entirely until someone intervenes.
Policy Bypass Surface Enforcement Gap, Derived-Object Leak	concept	Row & Column-Level Security	The set of objects and paths through which data protected by a row or column policy can be read without that policy being evaluated - typically derived objects refreshed under a privileged identity.
Policy Failure Mode Admission Fail-Open, Fail-Closed Policy	concept	Policy as Code	What an admission-time policy engine does when it cannot be reached - fail open and allow the change, or fail closed and block it - decided per policy class rather than globally, because a uniform answer is wr…
Polyglot Persistence	concept	Polyglot Persistence	Using different storage engines for different workloads within one system — justified by genuine workload divergence, and frequently not.
Port Exhaustion	concept	NAT & Egress	Running out of available source ports for outbound connections through a NAT device, causing new connections to fail while everything appears healthy.