How Durable Objects and D1 Work: A Deep Dive with Cloudflare’s Josh Howard

Josh Howard, Senior Engineering Manager at Cloudflare, joins me to explain how Durable Objects and D1 work under the hood—and why Cloudflare’s approach to stateful serverless infrastructure is so unique. We get into V8 isolates, replication models, routing strategies, and even upcoming support for containers.

Want to learn more about SQLite? Check out my SQLite course: https://highperformancesqlite.com/?ref=podcast

Follow Josh:
Twitter: https://twitter.com/ajoshhoward
LinkedIn: https://www.linkedin.com/in/joshthoward

Follow Aaron:
Twitter: https://twitter.com/aarondfrancis
LinkedIn: https://www.linkedin.com/in/aarondfrancis
Website: https://aaronfrancis.com - find articles, podcasts, courses, and more.

Database school on YouTube: https://www.youtube.com/playlist?list=PLI72dgeNJtzqElnNB6sQoAn2R-F3Vqm15
Database school audio only: https://databaseschool.transistor.fm

Chapters
00:00 - Intro
00:37 - What is a Durable Object?
01:43 - Cloudflare’s serverless model and V8 isolates
03:58 - Why stateful serverless matters
05:14 - Durable Objects vs Workers
06:22 - How routing to Durable Objects works
08:01 - What makes them "durable"?
08:51 - Tradeoffs of colocating compute and state
10:58 - Stateless Durable Objects
12:49 - Waking up from sleep and restoring state
16:15 - Durable Object storage: KV and SQLite APIs
18:49 - Relationship between D1, Workers KV, and DOs
20:34 - Performance of local storage writes
21:50 - Storage replication and output gating
24:15 - Lifecycle of a request through a Durable Object
26:46 - Replication strategy and long-term durability
31:25 - Placement logic and sharding strategy
36:35 - Use cases: agents, multiplayer games, chat apps
40:33 - Scaling Durable Objects
41:14 - Globally unique ID generation
43:22 - Named Durable Objects and coordination
46:07 - D1 vs Workers KV vs Durable Objects
47:50 - Outerbase acquisition and DX improvements
49:49 - Querying durable object storage
51:20 - Developer Week highlights and new features
52:44 - Read replicas and sticky sessions
53:49 - Containers and the future of routing
56:47 - Deployment regions and infrastructure expansion
57:43 - Hiring and how to connect with Josh