Intermediate code explainers

python

from flask import Blueprint, request, jsonify, abort
from sqlalchemy import update
 
from .models import db, Document

Optimistic locking in a Flask PATCH endpoint

optimistic-locking concurrency rest-api

Intermediate 7 steps

php

class Cart extends Model
{
    protected $fillable = ['user_id'];

Modeling a shopping cart in Laravel

eloquent relationships domain-model

Intermediate 7 steps

ruby

module Terminal
  module Color
    CODES = {
      black: 30, red: 31, green: 32, yellow: 33,

Building an ANSI color DSL in Ruby

metaprogramming monkey-patching ansi-escapes

Intermediate 9 steps

java

@Service
public class WebhookDedupService {
 
    private static final Logger log = LoggerFactory.getLogger(WebhookDedupService.class);

Idempotent webhooks with Redis in Spring

idempotency redis deduplication

Intermediate 7 steps

rust

use axum::{
    body::Body,
    extract::State,
    http::{Request, StatusCode},

A sliding-window rate limiter in Axum

rate-limiting middleware sliding-window

Intermediate 10 steps

go

package useragent
 
import (
	"regexp"

Parsing user-agent strings in Go

regex string-parsing ordering

Intermediate 7 steps

python

import os
import re
from flask import Blueprint, request, Response, abort

HTTP range requests for video streaming in Flask

http-range-requests streaming generators

Intermediate 8 steps

python

from io import BytesIO
from flask import Blueprint, abort, send_file
from reportlab.lib.pagesizes import LETTER
from reportlab.lib.units import inch

Streaming a generated PDF from a Flask route

pdf generation in-memory buffer file download

Intermediate 8 steps

javascript

function mergeDateRanges(ranges) {
  const parsed = ranges
    .map(({ start, end }) => ({
      start: new Date(start),

Merging overlapping date ranges

intervals sorting dates

Intermediate 8 steps

go

func ServeThumbnail(c *gin.Context) {
	raw := c.Param("token")
	sig := c.Query("sig")

A signed thumbnail endpoint in Gin

signed-urls image-processing http-handler

Intermediate 9 steps

php

<?php
 
namespace App\Services;

Throttling login attempts in Laravel

rate-limiting authentication security

Intermediate 6 steps

ruby

class ReportingQuery
  def initialize(scope = ApplicationRecord)
    @scope = scope
  end

Routing heavy reports to a read replica in Rails

read-replica database-roles query-object

Intermediate 6 steps

rust

use hmac::{Hmac, Mac};
use sha2::Sha256;
use subtle::ConstantTimeEq;

HMAC signing and constant-time verify in Rust

hmac cryptography constant-time

Intermediate 7 steps

typescript

import { Directive, ElementRef, HostListener, Renderer2, forwardRef } from '@angular/core';
import { ControlValueAccessor, NG_VALUE_ACCESSOR } from '@angular/forms';
 
@Directive({

Building a phone-mask ControlValueAccessor in Angular

directives control-value-accessor input-masking

Intermediate 8 steps

python

from celery import shared_task, signature
from django.core.mail import send_mail
 
from .models import Report, ReportExport

Chaining Celery tasks in Django

asynchronous tasks task chaining retries

Intermediate 8 steps

javascript

'use server'
 
import { z } from 'zod'
import { revalidatePath } from 'next/cache'

Handling form submits with Next.js Server Actions

server-actions validation form-handling

Intermediate 7 steps

go

package middleware
 
import (
	"hash/fnv"

A percentage feature-rollout middleware in Gin

feature-flags middleware hashing

Intermediate 6 steps

php

<?php
 
namespace App\Http\Requests;

Validating nested order payloads in Laravel

validation authorization nested-data

Intermediate 8 steps