Code Explainers

Intermediate code explainers

javascript
async function fetchAllPages(baseUrl, { pageSize = 100, headers = {} } = {}) {
  const results = [];
  let cursor = null;
 

Cursor-based pagination with fetch

pagination async-await fetch
Intermediate 6 steps
rust
use std::collections::HashMap;
 
pub fn word_frequencies(text: &str) -> HashMap<String, usize> {
    let mut counts: HashMap<String, usize> = HashMap::new();

Counting and ranking words in Rust

hashmap iterators sorting
Intermediate 7 steps
php
<?php
 
namespace App\Security;
 

A fixed-window rate limiter on APCu

rate-limiting fixed-window caching
Intermediate 8 steps
python
from flask import Blueprint, render_template, redirect, url_for, flash
from flask_login import login_required, current_user
from flask_wtf import FlaskForm
from wtforms import StringField, TextAreaField, SubmitField

Handling a post form with a Flask Blueprint

blueprints form-validation post-redirect-get
Intermediate 7 steps
go
package storage
 
import (
	"bufio"

Streaming file downloads safely in Go

http streaming path-traversal
Intermediate 7 steps
typescript
type SearchResult = {
  id: string;
  title: string;
};

Cancelling stale searches with AbortController

abortcontroller cancellation async
Intermediate 7 steps
java
public class WorkPipeline {
    private final BlockingQueue<Task> queue = new LinkedBlockingQueue<>(1000);
    private static final Task POISON = new Task(-1, null);
    private final ExecutorService consumers = Executors.newFixedThreadPool(4);

A producer-consumer pipeline in Java

concurrency producer-consumer blocking-queue
Intermediate 8 steps
ruby
class OrderConfirmationJob < ApplicationJob
  queue_as :mailers
 
  retry_on Net::OpenTimeout, wait: :polynomially_longer, attempts: 5

Resilient background jobs in Rails

background-jobs retries idempotency
Intermediate 8 steps
rust
use std::error::Error;
use std::fmt;
 
#[derive(Debug)]

Building a typed error enum in Rust

error-handling enums trait-implementation
Intermediate 9 steps
php
class PostController extends Controller
{
    public function index(Request $request)
    {

Eager loading without N+1 in Laravel

eager-loading n+1 query-builder
Intermediate 9 steps
python
import random
import time
import logging
from functools import wraps

A retry decorator with exponential backoff

decorators retry exponential-backoff
Intermediate 6 steps
go
package webhooks
 
import (
	"crypto/hmac"

Verifying GitHub webhooks in Gin

hmac webhooks middleware
Intermediate 6 steps
rust
use std::time::Duration;
 
use axum::{routing::get, Router};
use tokio::net::TcpListener;

Graceful shutdown in an Axum server

graceful-shutdown signal-handling async
Intermediate 8 steps
python
from django.db import models
from django.utils import timezone
 
 

How soft deletes work in Django

soft-delete querysets managers
Intermediate 10 steps
php
class PostController extends Controller
{
    public function index(Request $request): AnonymousResourceCollection
    {

Filtered, paginated JSON APIs in Laravel

eloquent query-builder api-resources
Intermediate 8 steps
javascript
import { useState, useEffect, useMemo } from 'react';
 
function useDebounce(value, delay = 300) {
  const [debounced, setDebounced] = useState(value);

Debounced search with cancellation in React

custom-hooks debounce abortcontroller
Intermediate 9 steps
java
package com.example.payments.config;
 
import jakarta.validation.constraints.Min;
import jakarta.validation.constraints.NotBlank;

Type-safe config with Spring records

configuration validation records
Intermediate 6 steps
ruby
module SoftDeletable
  extend ActiveSupport::Concern
 
  included do

How a soft-delete concern works in Rails

concerns soft-delete scopes
Intermediate 8 steps