Building the Next Evolution of Cloud Networks at Slack

This post details the "Whitecastle" project, a network architecture redesign at Slack. It introduces the use of AWS Shared VPCs to overcome AWS rate-limiting issues and manage IP spaces across multiple child accounts. It also describes the implementation of AWS Transit Gateway Inter-Region Peering to enable communication between different AWS regions, with an automated Terraform-based approach for managing peering connections and route tables. A "Whitecastle Network Tester" application is introduced for real-time network connectivity validation and monitoring. Finally, it outlines an incremental migration strategy for services to adopt the new network architecture.