Glossary

Optimistic locking

A write checks that the data version still matches the one previously read. Conflicts require a deliberate retry decision; do not blindly overwrite another change.

OrbStack

A macOS environment for Docker containers and Linux machines. It can be an alternative to Docker Desktop. The selected Docker context must target the engine intended for the lab.

Outbox

Record the intent to send a message in the same transaction as the business change. A worker delivers it later. Delivery may repeat, so the recipient still needs idempotency.

OWASP

OWASP

Open Worldwide Application Security Project

An organization and open resources supporting application security. The Top 10 helps identify risk categories but is not a complete audit of a particular system.

Pagination

Fetching results in parts. Define stable ordering and behaviour under data changes; offset and keyset pagination have different costs and properties.

Parallelism

Actual simultaneous execution, for example on multiple CPU cores. Not all concurrent work is parallel, and additional threads may add overhead.

pdb — Python debugger

pdb

Python Debugger

A Python standard-library module for pausing a program, inspecting variables and stepping through lines. python -m pdb runs a file under the debugger. Lowercase pdb is this module; uppercase PDB in Kubernetes is PodDisruptionBudget, a different concept.

Percentile

A threshold below which a specified fraction of observations falls. p95 is not an average; report request count, errors and load conditions alongside latency.

Performance

The relationship between completed work, latency and resources under defined conditions. Start with a hypothesis and measurement; comparisons need aligned workloads and error checks.

PersistentVolume

PV

Persistent Volume

Kubernetes resource describing storage. Its lifecycle and reclaim policy affect data; deleting a Pod is not the same as deleting its volume.

PersistentVolumeClaim

PVC

Persistent Volume Claim

A workload’s storage claim. Size, access mode and storage class affect PV binding. Pending may indicate no suitable provisioner or storage resource.

Personally identifiable information

PII

Personally Identifiable Information

Data that can identify a person directly or when combined with other data. Minimize what enters logs and AI context; replacing a name with an identifier does not ensure anonymity.

Pessimistic locking

An operation reserves access through a lock before changing a resource. Keep lock duration short and avoid external I/O within that transaction.

PHP

PHP

PHP: Hypertext Preprocessor

A language used for server applications, among other uses. Compare the language separately from execution models: FPM and Octane workers have different application lifecycles.

PHP array shape

A description of known keys and their types, such as array{price: int, name?: string} in PHPDoc. It helps detect invalid reads statically; it is not an input parser or a guarantee about HTTP data.

PHP Data Objects

PDO

PHP Data Objects

A PHP interface to database drivers and prepared statements. Parameters protect values, not arbitrary dynamically constructed table or column names.

PHP-FPM

FPM

FastCGI Process Manager

PHP-FPM

PHP FastCGI Process Manager

A manager for PHP processes serving FastCGI requests. The application lifecycle usually restarts per request, although worker processes themselves may be reused.

PHPDoc

Documentation comments describing parameter, return and data-structure types, among other details. Tools such as PHPStan use them for static analysis. A comment alone does not validate JSON at runtime.

pnpm

A JavaScript package manager. Align its version and pnpm-lock.yaml with the repository to avoid accidental dependency changes.

PodDisruptionBudget

PDB

Pod Disruption Budget

Limits voluntary disruptions for a set of Pods. It does not prevent every node failure and may block a planned node drain.

Polymorphism

Using different implementations through one contract. A valid substitution must preserve expected behaviour, not merely matching method names.

Prettier

A code/document formatter normalizing style so review can focus on changes rather than spacing.

Process Identifier

PID

Process Identifier

A process identifier within a system. It can be reused; it is not a durable job or user identity.

Profiling

Measurement of which functions use CPU time or memory under a defined workload. A profile explains process resource use but alone cannot establish the cause of database waiting or API throughput.

Projection

A read model derived from other data or events. Define freshness and rebuilding; losing it need not mean losing the source of truth.

Prometheus

A system that collects and stores metrics as labelled time series, usually by scraping an endpoint. A customer ID label increases series cardinality and may expose data.

Prompt injection

Untrusted text attempts to change the model’s task or rules. Treat file contents and tool results as data. Enforce permissions outside the model; a prompt alone is not a security boundary.

Proof Key for Code Exchange

PKCE

Proof Key for Code Exchange

An OAuth extension binding an authorization code to a client verifier. It does not replace redirect-URI, state or identity validation.

Property-based testing

Testing a rule across generated inputs, such as billed days covering a period and exceeding it by less than one day. The property and generator must match the contract. A framework may shrink a counterexample; randomness alone proves nothing.

Proxy pattern

An intermediary controls access to another object, for example through lazy loading. An apparently local operation may perform remote I/O; do not automatically equate it with a network proxy.