System design

Each of these walks through a system end to end, told as a company hitting the problem for real and making a decision at each step. Where there are numbers I have used real ones and linked the source.

Notes

• Designing a chat applicationDelivery guarantees, fanout for group chats, presence, and why WhatsApp moved off a thread per connection.
• Designing a media servicePresigned uploads, thumbnail generation without a queue service, and why file storage is a separate service from the chat app that uses it.
• Designing a multi-tenant RBAC serviceRoles, permissions, local vs. central authorization, policy-version revocation, and a working demo with production-shaped Terraform.

More coming as I work through them.

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