Terminology

384 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 areas384 Architecture Fundamentals16 Distributed Systems73 Data Architecture71 Cloud Architecture17 Networking13 API & Integration Architecture17 Reliability & Resilience16 Observability14 Performance & Capacity Engineering13 Security Architecture18 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 concept136 practice90 pattern81 case-study26 protocol19 tool19 metric13

71 terms shown.

Term	Kind	Topic	What it is
Backfill	practice	ETL & ELT	Re-running a pipeline over historical periods to populate new data or correct a past error, and the operation that proves whether a pipeline is well designed.
Bloom Filter	tool	Data Architecture	A compact probabilistic structure that answers "is this key definitely absent, or possibly present?" — no false negatives, tunable false positives.
Bloom Filter Cache Guard	pattern	Caching Strategies	Placing a Bloom filter in front of an expensive lookup so that keys which certainly do not exist never reach it.
Cache Invalidation	concept	Data Architecture	The problem of removing or refreshing cached data when the underlying source changes, and the reason caching is harder than it looks.
Cache Penetration	concept	Cache Invalidation	Repeated lookups for keys that do not exist, which miss the cache every time by definition and pass straight through to the store.
Cache Stampede Dog-piling, Thundering Herd on Cache	concept	Cache Invalidation	Many concurrent requests missing on the same expired key and all recomputing it simultaneously, converting one expiry into a load spike.
Cardinality Estimation	concept	Query Optimisation	The planner's prediction of how many rows each step of a query will produce — the input that determines every other choice it makes.
CDC Initial Snapshot	concept	Change Data Capture	The consistent full copy taken when a CDC pipeline starts, before streaming begins — and the step that determines whether the target is correct.
Change Data Capture CDC	pattern	Data Architecture	Publishing a stream of a database's row-level changes by reading its replication log, without modifying the application that owns it.
Covering Index Index-Only Scan	concept	Indexing	An index that contains every column a query needs, so the query is answered from the index without reading the table at all.
CQRS Command Query Responsibility Segregation	pattern	Data Architecture	Separating the model used to change state from the model used to read it, so each can be optimised independently.
Crypto-Shredding Cryptographic Erasure	pattern	Data Lifecycle & Retention	Encrypting each subject's data with its own key and destroying that key to render the data permanently unreadable, achieving deletion without deleting.
Data Catalog	tool	Data Governance	A searchable inventory of datasets with their schema, owner, meaning, freshness, quality and classification.
Data Contract	practice	Data Governance	An explicit, versioned, enforced agreement between a data producer and its consumers about schema, semantics, quality and change policy.
Data Lakehouse	concept	Data Architecture	A pattern that puts warehouse-style transactions, schema and governance on top of cheap open-format object storage.
Data Lineage	practice	Data Governance	A record of where each dataset came from, what transformed it, and what depends on it — traced at table and ideally column level.
Data Mesh	concept	Data Architecture	An organisational approach that gives domain teams ownership of their analytical data as a product, with a self-serve platform and federated governance.
Data Retention Policy	practice	Data Architecture	A defined rule for how long each class of data is kept, where, and what happens at the end of it.
Database Index	concept	Data Architecture	A secondary structure that lets the engine find rows without scanning, trading write cost and storage for read speed.
Database per Service	pattern	Polyglot Persistence	Each service owning its own datastore, with no other service reading or writing it directly.
Denormalisation	practice	Data Architecture	Deliberately duplicating data across records to make reads cheap, accepting the write-time cost of keeping copies in step.
Discord's Message Store Migrations	case-study	Data Architecture	Discord moved from MongoDB to Cassandra to ScyllaDB as message volume grew from millions to trillions, each time for a specific and different reason.
Document Store	tool	NoSQL Stores	A store that keeps semi-structured documents — typically JSON — retrievable by key and queryable by their contents.
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.
Event Sourcing	pattern	Data Architecture	Storing the full sequence of state-changing events as the system of record, and deriving current state by replaying them.
Event Store	tool	Event Sourcing	An append-only store of domain events organised into per-entity streams, serving as the system of record rather than as a log beside it.
Event Upcasting	pattern	Event Sourcing	Transforming an old event's stored form into the current shape as it is read, so historical events remain replayable after the schema changes.
Figma's Postgres Sharding	case-study	Data Architecture	Figma delayed sharding for years using replicas and vertical partitioning, then sharded Postgres horizontally without downtime using logical shards and a proxy layer.
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.
Graph Database	tool	NoSQL Stores	A store whose first-class citizens are nodes and the relationships between them, making multi-hop traversal cheap.
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.
Idempotent Pipeline	practice	ETL & ELT	A pipeline whose task can be re-run for the same input window any number of times and produce the same result.
Index Selectivity	metric	Indexing	The fraction of rows a predicate eliminates — the property that determines whether an index is worth using at all.
Indexing Strategy	practice	Data Architecture	Choosing the set of indexes a table carries by working backwards from its actual queries, and accepting the write cost that each one adds.
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.
Log-Based CDC	pattern	Change Data Capture	Capturing changes by reading the database's own write-ahead log, which sees every change with no load on the source and no application involvement.
Materialized View	pattern	Data Architecture	A precomputed, stored result of a query, refreshed on a schedule or from a change stream, read instead of recomputing.
Multi-Leader Replication Multi-Master, Active-Active Replication	pattern	Replication	Accepting writes at more than one node and replicating between them, which removes the single-primary bottleneck and introduces write conflicts.
Netflix's Recommendation Architecture	case-study	Data Architecture	Netflix splits personalisation into offline, nearline and online layers so that expensive computation happens ahead of time and the request path stays fast.
Normalisation Normal Forms	practice	Relational Modelling	Organising a schema so each fact is stored exactly once, removing the update anomalies that duplication creates.
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.
Open Table Format Apache Iceberg, Delta Lake, Apache Hudi	protocol	Data Lakes & Lakehouses	A metadata layer over files in object storage that supplies ACID transactions, schema evolution and time travel — the thing that turns a data lake into a lakehouse.
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.
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.
Pinterest's MySQL Sharding	case-study	Data Architecture	Pinterest sharded MySQL by embedding the shard ID inside every primary key, making any object's location computable from its ID alone with no lookup service.
Pipeline Orchestration	practice	ETL & ELT	Coordinating the execution of data tasks by dependency rather than by clock, with retries, backfill and observability built in.
Projection	pattern	CQRS	The process that consumes changes from the write side and maintains a read model, and the component where most CQRS bugs live.
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.
Query-Based CDC Polling CDC, Timestamp-Based CDC	pattern	Change Data Capture	Detecting changes by repeatedly querying for rows modified since the last run — simple, universally available, and lossy in specific ways.
Read Model Query Model, Projection Store	pattern	CQRS	A data structure shaped for a specific query rather than for the domain, maintained separately from the write model.
Read Replica	pattern	Data Architecture	A copy of a database that receives changes from the primary and serves read-only queries, spreading read load.
Replication Lag	metric	Replication	How far behind a replica is, measured in time or in log position — the quantity that determines how stale a replica read can be.
Right to Erasure Right to be Forgotten	concept	Data Lifecycle & Retention	A data subject's right to have their personal data deleted, and an obligation that reaches every copy an architecture has created.
Salesforce's Metadata-Driven Multi-Tenancy	case-study	Data Architecture	Salesforce serves every customer from shared infrastructure with a single physical schema, storing customer-specific data structures as metadata rather than as separate tables.
Schema Evolution	concept	Data Lakes & Lakehouses	Changing a table's structure over time while keeping existing data readable and existing consumers working.
Sharding Horizontal Partitioning	pattern	Data Architecture	Splitting one dataset across multiple independent databases by a partition key, so that each holds a disjoint subset.
Slowly Changing Dimension SCD	pattern	Data Warehousing	A strategy for handling attributes that change over time, deciding whether history is preserved and how facts attach to the correct version.
Snapshotting	pattern	Event Sourcing	Periodically storing an aggregate's computed state so it can be loaded without replaying its entire event history.
Star Schema	pattern	Data Warehousing	A dimensional model with one central fact table of measurements surrounded by denormalised dimension tables describing them.