Advanced code explainers

python

import base64
import json
from flask import Blueprint, request, jsonify, url_for, abort
from sqlalchemy import and_, or_

Cursor pagination in a Flask API

cursor-pagination keyset-pagination rest-api

Advanced 9 steps

rust

use axum::{
    extract::{Path, State},
    http::StatusCode,
    Json,

Distinguishing absent from null in an Axum PATCH

partial-update serde nullable-fields

Advanced 8 steps

rust

use std::collections::HashMap;
use std::future::Future;
use std::hash::Hash;
use std::sync::{Arc, Mutex};

Deduplicating concurrent work in Rust

concurrency deduplication async

Advanced 7 steps

typescript

import { Directive, ElementRef, EventEmitter, NgZone, OnDestroy, OnInit, Output } from '@angular/core';
 
interface Point {
  x: number;

Throttling pointer events with NgZone in Angular

change-detection requestanimationframe event-throttling

Advanced 8 steps

javascript

import OpenAI from 'openai';
 
const openai = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });

Streaming OpenAI tokens from a Next.js edge route

streaming edge-runtime readablestream

Advanced 9 steps

typescript

import { Injectable } from '@angular/core';
import {
  ActivatedRouteSnapshot,
  DetachedRouteHandle,

A scroll-preserving RouteReuseStrategy in Angular

route-reuse scroll-restoration caching

Advanced 10 steps

typescript

import {
  Directive,
  ElementRef,
  EventEmitter,

An infinite-scroll directive in Angular

intersectionobserver directives performance

Advanced 7 steps

typescript

import {
  Component,
  ComponentRef,
  Injector,

Dynamic component rendering in Angular

dynamic-components viewcontainerref lifecycle-hooks

Advanced 7 steps

typescript

import { Directive, ElementRef, EventEmitter, inject, NgZone, OnDestroy, Output } from '@angular/core';
 
@Directive({
  selector: '[appResizeDebounced]',

A debounced resize directive in Angular

debounce change-detection host-bindings

Advanced 7 steps

python

from django.db import transaction
from django.db.models import F
from django.http import JsonResponse
from django.views.decorators.http import require_POST

Safely reordering tasks with a Django action

transactions row-locking validation

Advanced 8 steps

rust

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

Streaming a DB migration with Axum

streaming keyset-pagination backpressure

Advanced 8 steps

python

import heapq
 
 
class MovingMedian:

Running median with two heaps

heaps streaming invariants

Advanced 8 steps

ruby

require "thread"
 
class ConnectionPool
  class TimeoutError < StandardError; end

Building a thread-safe connection pool in Ruby

concurrency resource-pooling mutex

Advanced 8 steps

go

package dedup
 
import (
	"hash/fnv"

A rolling Bloom filter deduper in Go

bloom-filter deduplication concurrency

Advanced 7 steps

rust

use axum::{
    extract::{FromRequestParts, Path, Query},
    http::{request::Parts, StatusCode},
    response::{IntoResponse, Redirect},

Signed download links as an Axum extractor

hmac custom-extractor authentication

Advanced 9 steps

java

@Service
@RequiredArgsConstructor
public class ExchangeRateService {

Request-scoped rate caching in Spring

request-scope caching memoization

Advanced 6 steps

go

package server
 
import (
	"net/http"

Rate limiting HTTP handlers with a token bucket

rate-limiting token-bucket middleware

Advanced 7 steps

java

public final class CircuitBreaker {
 
    private enum State { CLOSED, OPEN, HALF_OPEN }

How a circuit breaker guards failing calls

state-machine resilience concurrency

Advanced 7 steps