Code Explainers

Intermediate code explainers

php
<?php
 
declare(strict_types=1);
 

Counting business days in PHP

dates immutability hash-lookup
Intermediate 7 steps
java
@Configuration
public class PaymentGatewayClientConfig {
 
    @Bean

Building a resilient RestClient in Spring

retry http-client backoff
Intermediate 9 steps
go
package handlers
 
import (
	"net/http"

Custom struct-level validation in Gin

validation struct-tags cross-field
Intermediate 7 steps
python
from django.db import models
from django.db.models import F, Sum, DecimalField
from django.db.models.functions import Coalesce
 

Recomputing order totals in Django

annotations aggregation custom-manager
Intermediate 9 steps
rust
use axum::{
    body::Body,
    extract::Request,
    http::{header::SET_COOKIE, HeaderValue},

Flash messages via Axum middleware

middleware shared-state cookies
Intermediate 8 steps
typescript
type ToastVariant = "info" | "success" | "warning" | "error";
 
interface Toast {
  id: string;

A self-dismissing toast store with dedup

observer-pattern deduplication timers
Intermediate 10 steps
php
<?php
 
namespace App\Services;
 

A cached settings service in Laravel

caching memoization cache-invalidation
Intermediate 8 steps
go
package config
 
import (
	"os"

Layered config resolution in Go

configuration closures higher-order-functions
Intermediate 8 steps
rust
use std::collections::HashSet;
use std::fs;
use std::path::{Path, PathBuf};
use std::thread;

Polling a directory for new files in Rust

polling filesystem callbacks
Intermediate 6 steps
ruby
require "erb"
 
class TemplateRenderer
  class MissingVariableError < StandardError; end

A safe ERB template renderer in Ruby

metaprogramming method_missing binding
Intermediate 10 steps
java
public final class RetryExecutor {
 
    private final int maxAttempts;
    private final Duration baseDelay;

Retry with exponential backoff in Java

retry exponential-backoff jitter
Intermediate 7 steps
ruby
class ReverseGeocodeSignupJob < ApplicationJob
  queue_as :default
 
  retry_on Geocoder::OverQueryLimitError, wait: 5.minutes, attempts: 3

How Rails jobs handle reverse geocoding

background-jobs error-handling geocoding
Intermediate 7 steps
java
@Service
public class ProductLookupService {
 
    private final ProductRepository productRepository;

How Spring caching layers a product lookup

caching cache-eviction fallback
Intermediate 8 steps
javascript
import type { MetadataRoute } from 'next'
import { db } from '@/lib/db'
 
const URLS_PER_SITEMAP = 50_000

Sharding a large sitemap in Next.js

sitemap pagination seo
Intermediate 6 steps
typescript
type RGB = readonly [number, number, number];
 
interface ColorStop {
  offset: number;

Interpolating a color gradient in TypeScript

interpolation data-visualization color
Intermediate 8 steps
php
final class FormEditorHistory
{
    private SplStack $undoStack;
    private SplStack $redoStack;

Undo/redo with two stacks in PHP

undo-redo stack state-management
Intermediate 9 steps
go
package api
 
import (
	"encoding/json"

Safely decoding JSON in a Go HTTP handler

http json-decoding input-validation
Intermediate 8 steps
php
<?php
 
namespace App\Reports;
 

Bucketing spending by time period in Laravel

aggregation date-bucketing collections
Intermediate 9 steps