Code Explainers

Browse the library

php 
<?php
 
namespace App\RateLimiting;
 

Sliding-window rate limiting with Redis sorted sets

rate-limiting redis sorted-sets
Advanced 8 steps
typescript 
type Semver = {
  major: number;
  minor: number;
  patch: number;

Parsing and comparing semver strings in TypeScript

parsing regular-expressions comparison
Intermediate 9 steps
ruby 
class CircuitBreaker
  class OpenCircuitError < StandardError; end
 
  def initialize(failure_threshold: 5, reset_timeout: 30, half_open_max: 1)

How a circuit breaker guards failing calls

state-machine fault-tolerance concurrency
Advanced 9 steps
javascript 
function formatPhoneNumber(value) {
  const digits = value.replace(/\D/g, '').slice(0, 10);
  const parts = [];
 

Building a live phone number input mask

input-masking regex dom-events
Intermediate 7 steps
python 
from flask import Blueprint, jsonify
from marshmallow import Schema, fields, validate, EXCLUDE
from webargs.flaskparser import use_args
 

Validating query params in Flask with webargs

validation schema query-building
Intermediate 10 steps
java 
public URI buildSearchUri(String query, int page, int size, List<String> tags) {
    UriComponentsBuilder builder = UriComponentsBuilder
            .fromUriString("https://api.example.com")
            .path("/v2/products/search")

Building URIs safely with UriComponentsBuilder in Spring

url-building builder-pattern encoding
Intermediate 5 steps
rust 
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum FileKind {
    Png,
    Jpeg,

Detecting file types by magic bytes in Rust

pattern-matching byte-slices lookup-table
Intermediate 7 steps
go 
func (h *ExportHandler) BulkExport(c *gin.Context) {
	projectID := c.Param("projectID")
 
	reports, err := h.reports.ListByProject(c.Request.Context(), projectID)

Streaming a ZIP download in Gin

streaming zip-archive http-headers
Intermediate 8 steps
php 
<?php
 
namespace App\Models\Concerns;
 

How an Auditable trait logs Eloquent changes in Laravel

traits model-events polymorphic-relations
Intermediate 8 steps
php 
<?php
 
namespace App\Http\Controllers;
 

Server-Sent Events in Laravel

server-sent-events streaming long-polling
Advanced 9 steps
java 
@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
 

Real-time chat over STOMP WebSockets in Spring

websockets stomp messaging
Intermediate 8 steps
python 
import hashlib
import json
from fastapi import APIRouter, Request, Response, Depends, HTTPException, status
 

HTTP ETag caching in a FastAPI route

http-caching etag conditional-requests
Intermediate 9 steps
javascript 
import { NextResponse } from 'next/server';
 
const locales = ['en', 'fr', 'de', 'es'];
const defaultLocale = 'en';

Locale routing with Next.js middleware

middleware i18n content-negotiation
Intermediate 10 steps
ruby 
class ProjectsController < ApplicationController
  before_action :set_project, only: %i[show update destroy]
 
  def create

Scoping a Rails API controller to Current.account

multitenancy strong-parameters nested-attributes
Intermediate 7 steps
go 
package middleware
 
import (
	"crypto/sha256"

Deduplicating concurrent requests in Gin

singleflight request-coalescing middleware
Advanced 8 steps
rust 
use crossbeam_channel::{Receiver, Sender, select, tick};
use std::time::Duration;
 
pub enum Command {

A channel-driven worker loop in Rust

channels select message-passing
Intermediate 9 steps
typescript 
import { Component } from '@angular/core';
import {
  trigger,
  transition,

Staggered list animations in Angular

animations stagger enter-leave
Intermediate 10 steps
php 
<?php
 
namespace App\Actions\Imports;
 

Streaming CSV imports with Laravel batches

lazy-collections job-batching streaming
Advanced 9 steps