Code Explainers
Browse the library
ruby
module RequestTagging class Middleware def initialize(app) @app = app
Per-request context with CurrentAttributes in Rails
middleware
thread-safety
logging
Intermediate
7 steps
go
package hashring import ( "hash/crc32"
How consistent hashing works in Go
consistent-hashing
load-balancing
concurrency
Intermediate
8 steps
javascript
import { useReducer, useCallback } from 'react'; function historyReducer(state, action) { const { past, present, future } = state;
Undo/redo form state with a React reducer
undo-redo
reducer
immutability
Intermediate
10 steps
python
import hashlib from collections import defaultdict from pathlib import Path
Finding duplicate files by size then hash
hashing
file-io
deduplication
Intermediate
7 steps
php
<?php final class RememberMeCookie {
Signed remember-me cookies in PHP
authentication
hmac
cookies
Intermediate
8 steps
typescript
type Middleware<TIn, TOut> = (ctx: TIn) => Promise<TOut> | TOut; class Pipeline<TIn, TOut> { private constructor(private readonly run: Middleware<TIn, TOut>) {}
A type-safe async middleware pipeline
generics
type-safety
middleware
Advanced
9 steps
rust
use std::time::{Duration, Instant}; pub struct Ewma { alpha: f64,
A time-decayed moving average in Rust
exponential-smoothing
time-decay
state-machine
Intermediate
8 steps
java
@Component public class HeaderMergeFilter { private static final String PER_REQUEST_HEADERS = HeaderMergeFilter.class.getName() + ".headers";
Merging default and per-request headers in Spring
webclient
filters
http-headers
Intermediate
8 steps
ruby
class Spellchecker ALPHABET = ('a'..'z').to_a.freeze def initialize(dictionary)
Building a Norvig-style spellchecker in Ruby
edit-distance
levenshtein
dynamic-programming
Advanced
10 steps
go
package middleware import ( "net/http"
Wrapping Gin requests in a DB transaction
middleware
transactions
error-handling
Intermediate
8 steps
javascript
import { NextResponse } from 'next/server'; import { db } from '@/lib/db'; function csvCell(value) {
Streaming a CSV export in a Next.js route
streaming
csv
readablestream
Advanced
9 steps
python
from flask import Flask, request, g, jsonify from flask_babel import Babel, gettext as _, format_datetime from datetime import datetime
Per-request localization in Flask with Babel
i18n
content-negotiation
request-lifecycle
Intermediate
8 steps
php
<?php namespace App\Http\Middleware;
Caching HTTP responses with Laravel middleware
middleware
caching
http
Intermediate
8 steps
typescript
type Countdown = { days: number; hours: number; minutes: number;
Building a self-stopping countdown timer
date-math
closures
timers
Intermediate
9 steps
rust
use std::fs::File; use std::io::{Read, Seek, SeekFrom}; #[derive(Debug)]
Parsing an HTTP Range header in Rust
http-range
parsing
file-io
Intermediate
10 steps
java
import java.util.HashSet; import java.util.Set; public final class CollectionDiff<T> {
Diffing two collections with set operations
set-operations
immutability
generics
Intermediate
8 steps
ruby
class Order < ApplicationRecord belongs_to :customer has_many :line_items has_many :products, through: :line_items
How scopes compose in a Rails model
scopes
activerecord
subqueries
Intermediate
7 steps
go
package handlers import ( "encoding/base64"
Cursor pagination in a Gin handler
pagination
cursor
rest-api
Intermediate
8 steps