Intermediate terms
Consumer Groups
1
Consumer groups allow multiple consumers to process messages from a topic in parallel — each partition assigned to one consumer, enabling horizontal scaling without duplicate processing.
6mo ago
Messaging intermediate
Copy-on-Write (CoW) in PHP Arrays
PHP 7.0+
1
PHP arrays are not copied when assigned or passed to functions — they share the same internal buffer until one copy is modified. Only then does PHP perform a real copy. This makes reading large arrays cheap but silent mutations expensive.
6mo ago
PHP intermediate
CORS — Cross-Origin Resource Sharing
PHP 7.0+
A browser security mechanism that blocks JavaScript from making HTTP requests to a different origin — PHP APIs must send specific headers to allow cross-origin requests from permitted frontend origins.
6mo ago
Security intermediate
create_function() — The Dynamic Code Smell
PHP 4.0+
8
create_function() created anonymous functions from strings — deprecated PHP 7.2, removed PHP 8. It used eval() internally, risked code injection, and was always replaceable with proper closures.
6mo ago
PHP intermediate
Cross-Version Compatibility Testing
PHP 7.0+
Testing PHP code across multiple versions uses CI matrix builds, phpenv/phpbrew, Docker multi-version setups, and static analysis to catch compatibility issues before deployment.
6mo ago
PHP intermediate
CSS :has() Selector
CSS :has() is a parent selector — .card:has(.badge) matches a .card that contains a .badge — enabling styles that depend on children or siblings, which previously required JavaScript.
6mo ago
Frontend intermediate
callable vs Closure vs First-Class Callable
PHP 7.1+
PHP has three callable forms: loose callable (string/array), typed Closure, and PHP 8.1 first-class callables (strlen(...)) — prefer Closure or first-class callables for type safety.
6mo ago
PHP intermediate
Circular References & Memory Implications
PHP 5.3+
1
Circular references between objects prevent PHP's reference counting GC from freeing memory — PHP's cycle collector handles them but with overhead.
6mo ago
PHP intermediate
Classic Closure-in-Loop Bug (var vs let)
ES2015
The most common JavaScript closure bug: using var in a for loop captures the loop variable by reference so all callbacks see the final value — fixed by using let which creates a new binding per iteration.
6mo ago
JavaScript intermediate
Constructor Promotion + readonly Together
PHP 8.1+
PHP 8.1+ allows readonly in constructor promotion: public function __construct(public readonly string $name) — the cleanest way to write immutable value objects.
6mo ago
PHP intermediate
Custom Error Handlers (set_error_handler)
PHP 5.0+
2
set_error_handler() lets you replace PHP's default error handling with a custom callback — essential for logging, alerting, and graceful degradation.
6mo ago
PHP intermediate
Client-Side Sanitisation
ES2015
5
DOMPurify and the Sanitizer API remove dangerous HTML before insertion — complementing PHP's server-side htmlspecialchars for rich-text scenarios.
6mo ago
JavaScript intermediate
CSRF Token Handling in Fetch & Axios
ES2017
Including PHP-generated CSRF tokens in JavaScript requests — reading from meta tags or cookies and attaching to every state-changing request.
6mo ago
JavaScript intermediate
Cache Warming Strategies
PHP 5.0+
Pre-populating a cache before traffic arrives — preventing the cold-start thundering herd where every request misses a cold cache simultaneously after a deploy.
6mo ago
Performance intermediate
Character Encoding
PHP 5.0+
3
How text is stored as bytes — ASCII (128 chars), Latin-1 (256 chars), UTF-8 (1-4 bytes, backwards compatible), and UTF-16 are the key encodings developers encounter.
6mo ago
i18n intermediate
Circular Buffer / Ring Buffer
PHP 5.0+
1
A fixed-size array treated as circular — the write pointer wraps around when it reaches the end, overwriting the oldest data. Used for logs, audio streaming, and producer-consumer queues.
6mo ago
Data Structures intermediate
CLI Tools with argparse & Click
Python 3.6+
3
Building Python command-line tools — argparse (stdlib) for simple tools, Click (decorator-based) for complex CLIs with subcommands, type coercion, and better help formatting.
6mo ago
Python intermediate
Cloud CDN
4
CloudFront, Fastly, Cloudflare — caching at edge PoPs worldwide reducing latency and origin load.
6mo ago
Cloud intermediate
Cloud Cost Optimisation
2
Systematically reducing cloud spend without reducing capability — right-sizing instances, using reserved/spot pricing, eliminating waste, and architecting for cost from the start.
6mo ago
Cloud intermediate
Cloud Message Queues
Managed queue services — AWS SQS, Google Pub/Sub — durable scalable queuing without managing RabbitMQ infrastructure.
6mo ago
Cloud intermediate