codesnips

concurrency

python 
import uuid
from django.db import models


class Cart(models.Model):
    OPEN = "open"

Prevent Duplicate Order Submissions in Django with select_for_update Row Locking

django postgres concurrency
by codesnips 3 tabs
javascript 
class TokenBucket {
  constructor(capacity, refillPerSecond) {
    this.capacity = capacity;
    this.refillPerMs = refillPerSecond / 1000;
    this.tokens = capacity;
    this.lastRefill = Date.now();

Token Bucket Rate Limiter Middleware for Express with Per-Key Buckets

nodejs express rate-limiting
by codesnips 4 tabs
go 
package worker

import (
	"context"
	"errors"
	"log"

Fan-Out Worker Pool With Context Cancellation and Graceful Shutdown in Go

go concurrency goroutines
by codesnips 2 tabs
sql 
CREATE TABLE daily_metrics (
    id          BIGGENERATED ALWAYS AS IDENTITY PRIMARY KEY,
    tenant_id   BIGINT      NOT NULL,
    metric      TEXT        NOT NULL,
    day         DATE        NOT NULL,
    count       BIGINT      NOT NULL DEFAULT 0,

SQL upsert for counters (ON CONFLICT DO UPDATE)

postgres sql concurrency
by codesnips 3 tabs
python 
import asyncio
import time
from dataclasses import dataclass
from typing import Any, Dict

In-Memory TTL Cache for FastAPI Endpoints With a Cache-Key Builder Dependency

fastapi caching ttl
by codesnips 3 tabs
rust 
use std::sync::Arc;
use std::time::{Duration, Instant};
use tokio::sync::Mutex;
use tokio::time::sleep;

#[derive(Debug)]

Rate-Limiting Outbound HTTP with a Token Bucket in Rust (Tokio)

rust tokio rate-limiting
by codesnips 3 tabs
php 
<?php

namespace App\Http\Controllers;

use App\Models\Wallet;
use App\Services\WalletService;

Debit a Wallet Balance Safely with Row Locking in Laravel

laravel eloquent transactions
by codesnips 4 tabs
go 
package pipeline

import "context"

func generate(ctx context.Context, nums ...int) <-chan int {
	out := make(chan int)

Fan-Out/Fan-In Pipeline With Channels and Context Cancellation in Go

go concurrency channels
by codesnips 3 tabs
ruby 
class CounterFlushJob
  include Sidekiq::Job
  sidekiq_options queue: :counters, retry: 3

  def perform
    CounterBuffer.flush_all.each do |field, delta|

Coalesced Counter Cache with Redis Buffering and Nightly Reconciliation in Rails

rails counter-cache redis
by codesnips 4 tabs
typescript 
import { Queue } from "bullmq";
import { createHash } from "crypto";

export const connection = { host: "127.0.0.1", port: 6379 };

export interface ChargePayload {

BullMQ job idempotency via dedupe id

node redis background-jobs
by codesnips 3 tabs
ruby 
class DiscountCode < ApplicationRecord
  has_many :redemptions, dependent: :destroy

  enum discount_type: { percentage: 0, fixed: 1 }

  validates :code, presence: true, uniqueness: { case_sensitive: false }

Redeem Discount Codes in Rails with a Locking Service and Row-Level Guards

rails activerecord discounts
by codesnips 4 tabs
python 
import time
import uuid
from dataclasses import dataclass

import redis

Sliding-Window Per-User Rate Limiting With Redis and a Flask Decorator

rate-limiting redis flask
by codesnips 3 tabs