Slack
Communication
Slack

Cellular architecture enabling real-time messaging for millions of teams

Employees:2,500+
Revenue:$1.5B+
Founded:2013
HQ:San Francisco, CA
Key Metrics
Users65M+ weekly active users
Requests100K+
Uptime99.99%
Latency<50ms
Messages/Day1.5B+
Paid Customers200K+
Apps Installed2,600+
Tech Stack
React
PHP
Java
MySQL
Vitess
AWS
Apache Kafka
System Architecture

Cellular Architecture

Slack Real-Time Architecture

WebSocket-Powered Messaging

Client Applications

Desktop (Electron)
React, TypeScript
Mobile Apps
Native
Web App
React

Real-Time Layer

WebSocket Gateway
Java, Netty
Pub/Sub
Kafka

Core Services

Messages
PHP, MySQL
Channels
PHP, Vitess
Search
Java, Solr
Files
S3

Data Layer

Vitess/MySQL
Sharded
Redis
Caching
Kafka
Events
WebSocket

Key Components

WebSocket Gateway

Real-time bidirectional communication layer handling millions of concurrent connections

Java
Netty
WebSocket
Vitess Database Layer

Horizontal sharding solution for MySQL enabling massive scale

Vitess
MySQL
Go

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Sources

https://slack.engineering/https://github.com/slackhq

Last updated: 2024-12-01