API contract
The documented shape and semantics of requests/responses that callers depend on.
Handbook · glossary
Vocabulary with a job, not dictionary trivia.
Use these definitions to explain architecture. If a term does not help you predict behavior or place a responsibility, it is not yet useful knowledge.
Authentication
Establishing who a caller is from verifiable identity evidence.
Authorization
Deciding whether an authenticated identity may perform an action on a resource.
Cache
A stored copy/representation used to avoid repeating more expensive work; it requires freshness/invalidation rules.
CORS
A browser-enforced policy controlling whether script from one origin may read responses from another origin.
Dependency injection
Providing an object's collaborators from outside rather than constructing hidden dependencies internally.
DTO / transport schema
A boundary representation for data crossing HTTP or another transport; not automatically the same as database/domain type.
Idempotency
Property where repeating an operation has the same intended effect as performing it once.
Migration
Versioned, repeatable database schema change applied in controlled order.
Monorepo
One repository containing multiple applications/packages with explicit workspace relationships.
Optimistic update
Temporarily updating UI/cache before server confirmation, with rollback/reconciliation rules.
ORM
A library mapping application operations/types to relational database queries; it does not remove database semantics.
Process
A running program instance with memory/resources managed by the operating system.
Query key
TanStack Query identity for cached server data including every parameter that changes the result.
Repository pattern
A persistence boundary expressed in application/domain language when that separation earns its complexity.
Runtime validation
Checking actual values while the program runs; required for untrusted external data even in TypeScript.
Server Component
A React component in Next.js that executes on the server and can keep server-only code/data out of the client bundle.
State machine
Explicit model of allowed states and transitions, useful for long-running workflows and preventing impossible transitions.
Transaction
Database unit of work whose changes commit together or roll back together according to transactional guarantees.
Trust boundary
A place where data/control crosses between parties/layers with different trust assumptions and therefore requires verification/validation.