Terms starting with "D"
Dependency Injection in Python
Python 3.8+
A design technique where objects receive their collaborators from outside rather than constructing them internally, inverting who controls instantiation.
3mo ago
Python intermediate
Database Bulk Operations
PHP 7.0+
3
Process many rows in a single SQL statement or batched transaction instead of one round-trip per row, for far higher throughput.
3mo ago
Database intermediate
Database Query Result Streaming
PHP 8.0+
2
Processing large result sets row-by-row without loading the entire dataset into memory - essential for PHP CLI scripts handling millions of rows.
5mo ago
Database intermediate
DOM Clobbering
7
Attack where injected HTML elements with controlled `id` or `name` attributes overwrite JavaScript globals or document properties, weaponising script-less HTML injection into code execution.
CWE-79 OWASP A3:2021
5mo ago
Security advanced
6.5
Diffusion Models
1
A class of generative models that learn to reverse a gradual noising process — starting from pure noise and iteratively denoising into coherent images, audio or video; the core technique behind Stable Diffusion, Midjourney and DALL·E 3.
5mo ago
AI / ML advanced
Discriminated Unions
2.0
2
A union of types that each carry a shared literal field (the discriminant) allowing TypeScript to narrow exhaustively — the canonical way to model mutually exclusive states.
6mo ago
TypeScript intermediate
Dependency & Supply Chain Security
Protecting applications from malicious or vulnerable third-party packages — covering transitive dependencies, lock files, SRI hashes, CVE scanning, and supply chain attack vectors.
CWE-1357 OWASP A6:2021
6mo ago
Security intermediate
Docker HEALTHCHECK
4
A Dockerfile instruction that defines how Docker tests whether a container is healthy — enabling automatic restart and load balancer removal on failure.
6mo ago
DevOps intermediate
Dead Code Elimination
PHP 7.4+
3
A compiler and static analysis optimisation that identifies and removes code that can never be executed or whose result is never used.
6mo ago
Compiler intermediate
Dijkstra's Shortest Path Algorithm
PHP 5.3+
1
A greedy graph algorithm that finds the shortest path from a source node to all other nodes in a weighted graph with non-negative edge weights.
6mo ago
Algorithms advanced
Database Connection Pooling
2
Connection pooling reuses a fixed set of database connections across requests — eliminating the 50–200ms connection overhead on every request and limiting DB connection count.
6mo ago
Concurrency intermediate
Database Indexes
4
Data structures that allow the database engine to find rows matching a condition without scanning every row — the single most impactful performance optimisation available for read-heavy PHP applications.
6mo ago
Database intermediate
DateTimeImmutable vs DateTime
PHP 5.5+
DateTimeImmutable returns a new object for every modification — the original is never changed. DateTime modifies in place. Prefer DateTimeImmutable in all new code to avoid subtle bugs where shared date objects are accidentally mutated.
6mo ago
PHP beginner
Dead Letter Queue
1
A Dead Letter Queue (DLQ) captures messages that can't be processed — expired, malformed, or repeatedly failed — enabling later inspection and replay without losing data.
6mo ago
Messaging intermediate
Deadlock
3
A deadlock occurs when two or more processes each hold a resource the other needs — both wait forever. Prevention requires consistent lock ordering or timeouts.
6mo ago
Concurrency intermediate
Debugging PHP
PHP 5.0+
8
Systematic techniques for finding and fixing PHP bugs — from var_dump and error logs to Xdebug step-debugging, with the guiding principle of narrowing down where incorrect behaviour first appears.
6mo ago
PHP beginner
DI Containers — PHP-DI, Symfony & Laravel Compared
PHP 7.4+
4
A Dependency Injection container automates wiring of class dependencies — instead of manually constructing objects and their dependencies, the container reads type hints and builds the full object graph. PHP-DI, Symfony's DIC, and Laravel's service container are the main options.
6mo ago
PHP intermediate
Distributed Tracing
3
Distributed tracing tracks a request as it flows through multiple services — each service adds a span to a shared trace, giving end-to-end visibility into latency and failures.
6mo ago
Observability intermediate
DNF Types (PHP 8.2)
PHP 8.2+
PHP 8.2 DNF (Disjunctive Normal Form) types allow unions of intersections — (Countable&Iterator)|null — combining PHP 8.1 intersection types with union types.
6mo ago
PHP advanced
DOMDocument & XPath in PHP
PHP 5.0+
1
PHP's DOMDocument extension parses HTML and XML into a traversable tree. Combined with DOMXPath, you can query the document with XPath expressions — far more powerful than regex for extracting data from HTML.
6mo ago
PHP intermediate