docs: Add ScyllaDB as online store alternative (fixed DCO) (#3944)

Author: zseta

docs/SUMMARY.md

@@ -99,6 +99,7 @@
   * [MySQL (contrib)](reference/online-stores/mysql.md)
   * [Rockset (contrib)](reference/online-stores/rockset.md)
   * [Hazelcast (contrib)](reference/online-stores/hazelcast.md)
+  * [ScyllaDB (contrib)](reference/online-stores/scylladb.md)
 * [Providers](reference/providers/README.md)
   * [Local](reference/providers/local.md)
   * [Google Cloud Platform](reference/providers/google-cloud-platform.md)

docs/reference/online-stores/README.md

@@ -54,4 +54,6 @@ Please see [Online Store](../../getting-started/architecture-and-components/onli
 [hazelcast.md](hazelcast.md)
 {% endcontent-ref %}
 
-
+{% content-ref url="scylladb.md" %}
+[scylladb.md](scylladb.md)
+{% endcontent-ref %}

docs/reference/online-stores/scylladb.md

@@ -0,0 +1,94 @@
+# ScyllaDB Cloud online store
+
+## Description
+
+ScyllaDB is a low-latency and high-performance Cassandra-compatible (uses CQL) database. You can use the existing Cassandra connector to use ScyllaDB as an online store in Feast.
+
+The [ScyllaDB](https://www.scylladb.com/) online store provides support for materializing feature values into a ScyllaDB or [ScyllaDB Cloud](https://www.scylladb.com/product/scylla-cloud/) cluster for serving online features real-time.
+
+## Getting started
+
+Install Feast with Cassandra support:
+```bash
+pip install "feast[cassandra]"
+```
+
+Create a new Feast project:
+```bash
+feast init REPO_NAME -t cassandra
+```
+
+### Example (ScyllaDB)
+
+{% code title="feature_store.yaml" %}
+```yaml
+project: scylla_feature_repo
+registry: data/registry.db
+provider: local
+online_store:
+    type: cassandra
+    hosts:
+        - 172.17.0.2
+    keyspace: feast
+    username: scylla
+    password: password
+```
+{% endcode %}
+
+### Example (ScyllaDB Cloud)
+
+{% code title="feature_store.yaml" %}
+```yaml
+project: scylla_feature_repo
+registry: data/registry.db
+provider: local
+online_store:
+    type: cassandra
+    hosts:
+        - node-0.aws_us_east_1.xxxxxxxx.clusters.scylla.cloud
+        - node-1.aws_us_east_1.xxxxxxxx.clusters.scylla.cloud
+        - node-2.aws_us_east_1.xxxxxxxx.clusters.scylla.cloud
+    keyspace: feast
+    username: scylla
+    password: password
+```
+{% endcode %}
+
+
+The full set of configuration options is available in [CassandraOnlineStoreConfig](https://rtd.feast.dev/en/master/#feast.infra.online_stores.contrib.cassandra_online_store.cassandra_online_store.CassandraOnlineStoreConfig).
+For a full explanation of configuration options please look at file
+`sdk/python/feast/infra/online_stores/contrib/cassandra_online_store/README.md`.
+
+Storage specifications can be found at `docs/specs/online_store_format.md`.
+
+## Functionality Matrix
+
+The set of functionality supported by online stores is described in detail [here](overview.md#functionality).
+Below is a matrix indicating which functionality is supported by the Cassandra plugin.
+
+|                                                           | Cassandra |
+| :-------------------------------------------------------- | :-------- |
+| write feature values to the online store                  | yes       |
+| read feature values from the online store                 | yes       |
+| update infrastructure (e.g. tables) in the online store   | yes       |
+| teardown infrastructure (e.g. tables) in the online store | yes       |
+| generate a plan of infrastructure changes                 | yes       |
+| support for on-demand transforms                          | yes       |
+| readable by Python SDK                                    | yes       |
+| readable by Java                                          | no        |
+| readable by Go                                            | no        |
+| support for entityless feature views                      | yes       |
+| support for concurrent writing to the same key            | no        |
+| support for ttl (time to live) at retrieval               | no        |
+| support for deleting expired data                         | no        |
+| collocated by feature view                                | yes       |
+| collocated by feature service                             | no        |
+| collocated by entity key                                  | no        |
+
+To compare this set of functionality against other online stores, please see the full [functionality matrix](overview.md#functionality-matrix).
+
+## Resources
+
+* [Sample application with ScyllaDB](https://feature-store.scylladb.com/stable/)
+* [ScyllaDB website](https://www.scylladb.com/)
+* [ScyllaDB Cloud documentation](https://cloud.docs.scylladb.com/stable/)