Glossary

Azure Kubernetes Service

AKS

Azure Kubernetes Service

Azure-managed Kubernetes. A managed control plane does not remove responsibility for application behavior, access and node costs.

Backend for Frontend

BFF

Backend for Frontend

A backend tailored to a particular client. Justify it through distinct client needs; avoid duplicating domain rules in it.

Backfill

Populating existing data into a new format or column. It must account for concurrent writes and resumption after interruption.

Backoff and jitter

A delay between retries, often increasing after repeated failures. Random jitter reduces the chance of many clients retrying at exactly the same instant.

Backpressure

When a consumer is slower, the producer limits its rate or in-flight work. An unbounded queue merely moves the problem into memory and latency.

Backup and restore

A copy intended to recover data after loss or error. Its usefulness is demonstrated by restoration and data checks, not merely a successful file-creation message.

Backward compatibility

A new provider preserves existing clients’ expectations about data shape and meaning. Unit or status changes can break clients despite valid JSON.

Behaviour testing

Checking specified behaviour with concrete cases. A useful test distinguishes the intended rule from a particular bug; passing the reference does not prove learner independence.

Behavioural contract

A promise of allowed inputs, results and side effects. A shared contract test can reject correctly typed code with incorrect behaviour.

Blackfire

An optional PHP and Python profiler for examining a selected request or command and comparing profiles. It needs a separate service and configuration; local exercises do not require it.

Bootstrap

Initial setup of controllers, access and sources needed to reconstruct a system. Git alone does not answer where the secret-decryption key comes from.

Boundary-value testing

Testing inputs at and beside a rule boundary. For a maximum length of 80, testing 80 and 81 distinguishes the correct limit from one that is too tight or too loose. An ordinary value away from the boundary does not establish this.

Breakpoint

A debugger stop point for inspecting selected values and stepping through execution. State dumps can expose sensitive data.

Builder

Collect options in stages and create a finished object with build. Validity still belongs at the finished-object boundary; compare constructors or named arguments for small configurations.

CA — certificates or scaling

CA

Certificate Authority / Cluster Autoscaler

In TLS and RDS: Certificate Authority, an issuer signing certificates. Clients validate the trust chain and server name. In Kubernetes scaling CA may mean Cluster Autoscaler, a different mechanism.

Cache

A copy of data or computed results kept for faster access. Define the source of truth, expiry, invalidation and limits; a successful cache read can still be stale.

Callback

A function supplied to other code for that code to call. Passing a function differs from passing the result of executing it first. A callback need not be asynchronous.

Cancellation

A request to end work whose result is no longer needed. A cancellation signal does not guarantee execution stops or effects are undone; check cleanup and I/O-client behaviour.

Certificate chain

Links a server certificate to a trusted authority through intermediate certificates. Encryption without server identity verification does not provide the same protection.

Chain of Responsibility

A handler decides whether to stop or delegate. Access checking before business effects requires an ordering test.

CIDR

CIDR

Classless Inter-Domain Routing

An address range written with a prefix length, such as 10.0.0.0/24. The prefix defines the network part. Overlapping ranges complicate network connectivity.

Circuit breaker

A mechanism temporarily refusing calls to a frequently failing dependency. It needs opening and recovery rules and observation; it does not replace timeouts or concurrency limits.

CLI

CLI

Command-Line Interface

An interface operated through terminal commands. Check working directory, arguments, exit status and whether a command reads or changes the environment.

Clock

A dependency supplying the current instant. A fixed clock tests an exact expiry boundary without sleep. Injecting a clock does not synchronize server clocks or remove transaction rules.

Closure

A function using variables from its enclosing scope. It can extend captured-data lifetime; retaining a request in a persistent worker needs care.

Cluster Autoscaler

Adjusts node capacity to Pod scheduling needs on supported infrastructure. HPA changes application replica count; that is a different scaling layer.

CNI

CNI

Container Network Interface

An interface for container-network integration. In Kubernetes, the chosen network implementation affects whether and how NetworkPolicy restricts traffic.

COALESCE

COALESCE is a SQL expression name, not an abbreviation.

A SQL expression returning the first non-NULL value. It does not compare freshness; an old non-null value can mask a newer value in another column.

Cohesion

How closely a module’s elements serve the same purpose and change for the same reason. It is not a class-count metric.

Collection

A structure holding multiple elements, such as a list, set or map. Choose it for ordering, duplicates, lookup and mutability rather than syntax alone.