Advanced code explainers

typescript

type Doc = { id: string; title: string; body: string };
 
type Posting = { docId: string; frequency: number; positions: number[] };

Building a TF-IDF search index

inverted-index tf-idf tokenization

Advanced 9 steps

go

package routing
 
import (
	"net/http"

Region-aware upstream routing in Gin

middleware concurrency load-balancing

Advanced 8 steps

rust

use axum::{
    extract::{FromRef, FromRequestParts, State},
    http::{header::ACCEPT_LANGUAGE, request::Parts, StatusCode},
    response::{IntoResponse, Response},

A custom Accept-Language extractor in Axum

extractors internationalization http-headers

Advanced 8 steps

python

import functools
import inspect
from typing import get_type_hints, get_origin, get_args, Union

A runtime type checker from annotations

decorators runtime-validation type-hints

Advanced 8 steps

java

public final class ThrottledLogger {
 
    private final Logger delegate;
    private final long windowMillis;

Rate-limiting log spam with per-message windows

concurrency rate-limiting throttling

Advanced 8 steps

python

import hashlib
import json
from functools import wraps
from flask import g, request, jsonify, current_app

Building an idempotency decorator in Flask

idempotency decorators redis

Advanced 7 steps

typescript

import {
  CallHandler,
  ConflictException,
  ExecutionContext,

Idempotent POST requests in NestJS with Redis

idempotency interceptor redis

Advanced 7 steps

rust

use std::sync::Mutex;
use std::time::{Duration, Instant};
 
#[derive(Debug, Clone, Copy, PartialEq)]

Building a circuit breaker in Rust

circuit-breaker state-machine concurrency

Advanced 8 steps

java

public final class ChunkSorter {
 
    private static final int MAX_LINES_PER_CHUNK = 100_000;

External merge sort in Java

external-sort merge-sort priority-queue

Advanced 10 steps

rust

use axum::{
    async_trait,
    extract::FromRequestParts,
    http::{request::Parts, StatusCode},

A proof-of-work extractor in Axum

proof-of-work extractors hashing

Advanced 9 steps

go

func StreamLogs(c *gin.Context) {
	path := c.Query("file")
	if path == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "missing file parameter"})

Streaming a live log tail with SSE in Gin

server-sent-events streaming channels

Advanced 10 steps

typescript

import { useCallback, useRef, useState } from "react";
 
interface VirtualListProps<T> {
  items: T[];

How a virtualized list renders in React

virtualization windowing performance

Advanced 7 steps

typescript

import {
  createParamDecorator,
  ExecutionContext,
  UnauthorizedException,

A signed-cookie param decorator in NestJS

custom-decorators hmac timing-safe-comparison

Advanced 8 steps

python

from datetime import datetime, timezone
 
from flask import abort
from sqlalchemy import Column, DateTime

Soft deletes with a custom SQLAlchemy Query in Flask

soft-delete mixin query-subclass

Advanced 7 steps

typescript

import {
  CallHandler,
  ExecutionContext,
  Injectable,

Deduping in-flight requests in NestJS

interceptor request-deduplication rxjs

Advanced 6 steps

typescript

import {
  Component,
  ContentChildren,
  QueryList,

Building a content-projected wizard in Angular

content-projection templateref querylist

Advanced 9 steps

java

@Component
public class IdempotencyFilter extends OncePerRequestFilter {
 
    private final StringRedisTemplate redis;

Building an idempotency filter with Redis in Spring

idempotency redis distributed-locking

Advanced 10 steps

java

@Configuration
public class DataLoaderConfig {
 
    @Bean

Batching GraphQL queries with DataLoaders in Spring

graphql batching n+1-problem

Advanced 8 steps