codesnips

concurrency

sql 
-- Step 1: add the column nullable, no default.
-- Catalog-only change in Postgres 11+, returns instantly.
ALTER TABLE orders
  ADD COLUMN currency text;

-- Optional: keep the lock attempt bounded so a long-running

SQL migration safety: add column nullable, backfill, then constrain

postgres migrations reliability
by codesnips 3 tabs
java 
package com.shop.payments.messaging;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;

public record PaymentEvent(

Idempotent Kafka Consumer With @KafkaListener and Manual Ack in Spring Boot

spring-boot kafka spring-kafka
by codesnips 3 tabs
typescript 
import { Injectable } from '@nestjs/common';

type Completed = { status: 'completed'; statusCode: number; body: unknown; expiresAt: number };
type InFlight = { status: 'in-flight'; startedAt: number };
type Record = Completed | InFlight;

Idempotency-Key Interceptor in NestJS to Debounce Duplicate Form Submissions

nestjs idempotency interceptor
by codesnips 4 tabs
go 
package middleware

import (
  "net/http"
  "sync/atomic"
)

Track in-flight requests with atomic counters

go observability concurrency
by Leah Thompson 1 tab
go 
package sse

type Broker struct {
	subscribers map[chan []byte]struct{}
	subscribe   chan chan []byte
	unsubscribe chan chan []byte

Server-Sent Events in Go with http.Flusher and Context Cancellation

sse streaming http
by codesnips 3 tabs
typescript 
import {
  Column,
  Entity,
  PrimaryGeneratedColumn,
  UpdateDateColumn,
  VersionColumn,

Optimistic Locking in NestJS with a TypeORM Version Column and Conflict Exception Filter

nestjs typeorm optimistic-locking
by codesnips 4 tabs
python 
import threading


class MinuteRingBuffer:
    def __init__(self, window_minutes=15):
        if window_minutes < 1:

Rolling Per-Minute Log Aggregation with a Ring Buffer

logging metrics observability
by codesnips 3 tabs
javascript 
const STORAGE_KEY = "auth.refreshToken";

let accessToken = null;
let refreshToken = localStorage.getItem(STORAGE_KEY);

const listeners = new Set();

Transparent JWT Refresh With a Single-Flight Axios Response Interceptor

axios interceptors jwt
by codesnips 3 tabs
ruby 
class LeaderboardCache
  TOP_KEY = "leaderboard:top".freeze
  STATS_KEY = "leaderboard:stats".freeze

  def top_players
    Rails.cache.fetch(TOP_KEY, expires_in: 5.minutes, race_condition_ttl: 15.seconds) do

Cache Stampede Protection with race_condition_ttl

rails caching performance
by codesnips 3 tabs
ruby 
class CreateWebhookEvents < ActiveRecord::Migration[7.1]
  def change
    create_table :webhook_events do |t|
      t.string :event_id, null: false
      t.string :source, null: false, default: "stripe"
      t.string :event_type, null: false

Idempotent Stripe Webhook Processing with a Unique Event Key in Rails

rails postgres webhooks
by codesnips 4 tabs
ruby 
class CreateOutboxEvents < ActiveRecord::Migration[7.1]
  def change
    create_table :outbox_events do |t|
      t.string :event_type, null: false
      t.string :aggregate_type, null: false
      t.string :aggregate_id, null: false

Transactional Outbox for Reliable Event Publishing

rails background-jobs reliability
by codesnips 4 tabs
typescript 
import { Prisma, PrismaClient } from "@prisma/client";

const prisma = new PrismaClient();

type TxClient = Prisma.TransactionClient;

Prisma transaction with retries for serialization errors

prisma postgres concurrency
by codesnips 3 tabs