Watch for changes to the given keys in the database. The returned stream is a ReadableStream that emits a new value whenever any of the watched keys change their versionstamp. The emitted value is an array of Deno.KvEntryMaybe objects, with the same length and order as the keys array. If no value exists for a given key, the returned entry will have a null value and versionstamp.

The returned stream does not return every single intermediate state of the watched keys, but rather only keeps you up to date with the latest state of the keys. This means that if a key is modified multiple times quickly, you may not receive a notification for every single change, but rather only the latest state of the key.

const db = await Deno.openKv();

const stream = db.watch([["foo"], ["bar"]]);
for await (const entries of stream) {
  entries[0].key; // ["foo"]
  entries[0].value; // "bar"
  entries[0].versionstamp; // "00000000000000010000"
  entries[1].key; // ["bar"]
  entries[1].value; // null
  entries[1].versionstamp; // null
}

The options argument can be used to specify additional options for the watch operation. The raw option can be used to specify whether a new value should be emitted whenever a mutation occurs on any of the watched keys (even if the value of the key does not change, such as deleting a deleted key), or only when entries have observably changed in some way. When raw: true is used, it is possible for the stream to occasionally emit values even if no mutations have occurred on any of the watched keys. The default value for this option is false.