Intermediate code explainers

java

public record TimeSlot(LocalDate day, LocalDateTime start, LocalDateTime end) {}
 
public class ScheduleAnalyzer {

Detecting calendar conflicts in Java

streams sorting sweep-line

Intermediate 8 steps

ruby

class EditorHistory
  MAX_DEPTH = 100
 
  def initialize(initial = "")

How undo/redo history works in Ruby

undo-redo state-management immutability

Intermediate 9 steps

python

import gzip
from fastapi import FastAPI, Request, Response
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.types import ASGIApp

Custom gzip middleware in FastAPI

middleware http-compression content-negotiation

Intermediate 9 steps

php

<?php
 
function streamFileWithRanges(string $path, ?string $rangeHeader): void
{

How HTTP range requests stream files in PHP

http-range-requests streaming partial-content

Intermediate 10 steps

rust

use std::collections::HashMap;
use std::sync::Arc;
 
use axum::body::Bytes;

A concurrent webhook dispatcher in Axum

trait-objects concurrency shared-state

Intermediate 9 steps

javascript

const UNIT_MULTIPLIERS = {
  ms: 1,
  s: 1000,
};

Parsing CSS durations into milliseconds

parsing regular-expressions validation

Intermediate 6 steps

java

@Controller
@RequestMapping("/employees")
public class EmployeeController {

Building a Spring MVC form controller

mvc form-handling validation

Intermediate 8 steps

go

func MergeSorted(a, b []int) []int {
	merged := make([]int, 0, len(a)+len(b))
	i, j := 0, 0

Merging two sorted slices in Go

two-pointers merge slices

Intermediate 6 steps

ruby

class Current < ActiveSupport::CurrentAttributes
  attribute :user, :request_id, :user_agent, :ip_address
 
  resets { Time.zone = nil }

Per-request audit trails with Current in Rails

thread-local-state auditing concerns

Intermediate 8 steps

python

from collections import Counter
 
import numpy as np
from PIL import Image

Extracting a color palette with K-means

clustering image-processing kmeans

Intermediate 7 steps

rust

use serde_json::{Map, Value};
 
pub fn merge_config(base: &mut Value, override_with: Value) {
    match (base, override_with) {

Deep-merging JSON config layers in Rust

recursion json pattern-matching

Intermediate 9 steps

javascript

class RequestDeduplicator {
  constructor(fetcher) {
    this.fetcher = fetcher;
    this.inFlight = new Map();

Deduplicating in-flight requests in JavaScript

promises caching async

Intermediate 6 steps

go

package retry
 
import (
	"errors"

How a retry budget caps retries in Go

rate-limiting sliding-window concurrency

Intermediate 7 steps

ruby

class Category < ApplicationRecord
  belongs_to :parent, class_name: "Category", optional: true
  has_many :children,
           -> { order(:position) },

Modeling a self-referential category tree in Rails

self-referential-association recursion tree-structure

Intermediate 9 steps

java

public final class PrefixSearch {
 
    private final String[] words;

Prefix search with binary search bounds

binary-search sorting range-query

Intermediate 9 steps

php

<?php
 
namespace App\Http\Controllers;

Processing refunds safely in Laravel

dependency injection validation database transactions

Intermediate 8 steps

python

import re
 
from flask_wtf import FlaskForm
from wtforms import StringField, TextAreaField, PasswordField

Cleaning form input with Flask-WTF filters

form validation input sanitization filters

Intermediate 8 steps

rust

use axum::{
    extract::{Path, State},
    http::HeaderMap,
    response::{Html, IntoResponse},

Building an HTMX-aware toggle handler in Axum

extractors htmx sqlx

Intermediate 8 steps