Render Cloudflare sites inside a Durable Object (opt-in deployment mode)

[swissky]

Problem

On Workers with D1, a cached page is fast (16 to 40 ms) and an uncached one is slow. Two things add up on a miss:

• An uncached page runs 14 to 25 D1 queries, many in sequence, at about 17 ms each. That is roughly 250 ms of waiting on the database while the Worker barely computes (64 to 159 ms CPU).
• Low-traffic sites mostly land on a cold isolate: 1.1 to 2.4 s TTFB in my tests, including about 250 ms to load a 19 MB bundle and 170 to 330 ms for the first D1 query. After 30 s without visitors the next request was cold again.

migrations: { runtime: "manual" }, Smart Placement with a KV object cache, and the existing durableObjects() adapter each help a little, but none removes both the per-query round trip and the cold isolate.

Use case

Small and medium sites on the Cloudflare templates: blogs, club sites, marketing sites. Most visitors hit the cache, but crawlers, editors, new regions and every page after a publish or deploy take the slow path. On scllauerz.ch, CoreDash counted 26% of real page loads at 875 ms TTFB or more over 31 days on D1, although zone analytics showed only 0.8% misses.

Current workarounds

I run three sites (scllauerz.ch, kevinkyburz.ch, linguadash.dev) on a prototype that needs no change to emdash or @emdash-cms/cloudflare 1.4.0. A tiny front Worker owns the Workers Cache and forwards misses over RPC to one Durable Object per site. The object runs the normal Astro SSR app with an in-process Kysely dialect on ctx.storage.sql, wired through database: { entrypoint, type: "sqlite" } and a custom cache.provider.

Uncached HTML median from zone analytics, 7 days on D1 against the days since the switch on November 8:

Site	D1	Durable Object
scllauerz.ch	2,837 ms	291 ms
kevinkyburz.ch (D1 with Placement + KV)	726 ms	204 ms
linguadash.dev	1,184 ms	450 ms

Known limits today: all misses go to one region, one object handles one request at a time (about 120 uncached renders per second on the demo, about 20 on kevinkyburz.ch, no errors up to 160 concurrent), sandboxed plugins don't work because the bridge reads env.DB (#1623, #4406, #4725), and there is no D1 Time Travel or wrangler d1 export. Full measurements: https://kevinkyburz.ch/blog/emdash-durable-object/

Your involvement

• I am requesting this capability.
• I am offering to champion the design in a feature plan or RFC.
• I am offering to implement it after the design is accepted.

I'd implement it in small PRs: shared DO SQLite execution code, the in-process dialect with workerd tests, the site object and front Worker in @emdash-cms/cloudflare marked experimental, then export/import and docs. The RFC lists 18 open questions, including whether this belongs in core at all. I'll open it as an RFC design PR and link it here.

~ 🤖 drafted with Claude Opus 5.5, reviewed by @swissky

[github-actions[bot]]

Design PR #4790 proposes proposals/cloudflare-site-durable-object.md for this Idea. Review of the design continues on the pull request.