Use Deno KV from a deployed Deno Deploy app: provision, read/write, and atomic transactions

Documented steps

1. Auth: Deno.openKv() uses the app's built-in Deploy runtime identity - no credential in code. Provision/assign via the deno deploy CLI (keyring login).
2. Provision a KV database for the org: deno deploy database provision my-kv --kind denokv; assign it: deno deploy database assign my-kv --app my-api.
3. Open in code: const kv = await Deno.openKv(); (same call locally; pass ":memory:" locally for ephemeral test stores).
4. Write: await kv.set(["users", id], { name }); keys are arrays of string/number/bigint/boolean.
5. Read: const entry = await kv.get(["users", id]); returns { key, value, versionstamp }; use kv.getMany([...]) (max 10 keys) or kv.list({ prefix }) for batches.
6. Delete: await kv.delete(["users", id]); no error if absent.
7. Atomic conditional write: await kv.atomic().check({ key, versionstamp }).set(key, value).commit();
8. Writes are strongly consistent; reads can opt into eventual consistency for lower latency. Production KV on Deploy is backed by FoundationDB.
9. Official docs: https://docs.deno.com/deploy/kv/ ; https://docs.deno.com/deploy/kv/transactions/ ; https://docs.deno.com/deploy/migration_guide/