Include new Scala engine and performance section in Kinesis docs (#1786)

Co-authored-by: HarshCasper <erbeusgriffincasper@gmail.com>

Author: gregfurman

content/en/references/configuration.md

@@ -239,6 +239,9 @@ Also see [OpenSearch configuration variables]({{< ref "configuration#opensearch"
 | `KINESIS_SHARD_LIMIT` | `100` (default), `Infinity` (to disable) | Integer value , causing the Kinesis API to start throwing exceptions to mimic the default shard limit. |
 | `KINESIS_ON_DEMAND_STREAM_COUNT_LIMIT` | `10` (default), `Infinity` (to disable) | Integer value , causing the Kinesis API to start throwing exceptions to mimic the default on demand stream count limit. |
 | `KINESIS_LATENCY` | `500` (default), `0` (to disable)| Integer value of milliseconds, causing the Kinesis API to delay returning a response in order to mimic latency from a live AWS call. |
+| `KINESIS_MOCK_PROVIDER_ENGINE` | `node` (default) \| `scala` | String value of `node` (default) or `scala` that determines the underlying build of Kinesis Mock. |
+| `KINESIS_MOCK_MAXIMUM_HEAP_SIZE` | `512m` (default) | JVM memory format string that sets the maximum memory size for the Kinesis Mock Scala server, corresponds to the JVM `-Xmx` flag. |
+| `KINESIS_MOCK_INITIAL_HEAP_SIZE` | `256m` (default) | JVM memory format string that sets the initial memory size for the Kinesis Mock Scala server, corresponds to the JVM `-Xms` flag. |
 
 ### Lambda
 

content/en/user-guide/aws/kinesis/index.md

@@ -171,14 +171,22 @@ $ awslocal kinesis put-record \
 
 You can fetch the CloudWatch logs for your Lambda function reading records from the stream, using AWS CLI or LocalStack Resource Browser.
 
-## Configuration
-
-| Variable | Description |
-| -------- | ----------- |
-| `KINESIS_ERROR_PROBABILITY` | Decimal value between `0.0` (default) and `1.0`. This environment variable enables you to inject `ProvisionedThroughputException` at random intervals in your application. While this won't provide insight into your application's overall throughput handling, it aids in testing your application's exception-handling capabilities. |
-| `KINESIS_SHARD_LIMIT` | Integer value (default: `100`) or `Infinity` (to disable). Use this variable to assess whether your application conforms to the assigned shard limit. Disabling this behavior requires explicitly setting `KINESIS_SHARD_LIMIT=Infinity`. |
-| `KINESIS_LATENCY` | Integer value in milliseconds (default: `500`) or `0` (to disable). Particularly useful for testing latency-sensitive applications. Since local Kinesis service lacks latency simulation, you can introduce artificial latency into your AWS calls using this variable. To disable this behavior, set `KINESIS_LATENCY=0`. |
-| `KINESIS_INITIALIZE_STREAMS` | **Deprecated.** Comma-delimited string with stream names, corresponding shard counts, and an optional region for initialization during startup. If no region is provided, the default region is used. For example, `KINESIS_INITIALIZE_STREAMS=my-first-stream:1,my-other-stream:2:us-west-2,my-last-stream:1`. In multi-account setups, the specified streams will be created for all accounts. |
+### Performance Tuning
+
+For high-volume workloads or large payloads, we recommend switching to the Scala engine via the `KINESIS_MOCK_PROVIDER_ENGINE=scala` flag, delivering up to 10x better performance compared to the default Node.js engine.
+
+Additionally, the following parameters can be tuned:
+
+- Increase `KINESIS_MOCK_MAXIMUM_HEAP_SIZE` beyond the default `512m` to reduce JVM memory pressure.
+- Increase `KINESIS_MOCK_INITIAL_HEAP_SIZE` beyond the default `256m` to pre-allocate more JVM heap memory.
+- Reduce `KINESIS_LATENCY` artificial response delays from the default `500` milliseconds (or disable entirely with `0`).
+
+Refer to our [Kinesis configuration documentation](https://docs.localstack.cloud/references/configuration/#kinesis) for more details on these parameters.
+
+{{< callout "note" >}}
+`KINESIS_MOCK_MAXIMUM_HEAP_SIZE` and `KINESIS_MOCK_INITIAL_HEAP_SIZE` are only applicable when using the Scala engine.
+Future versions of LocalStack will likely default to using the `scala` engine over the less-performant `node` version currently in use.
+{{< /callout >}}
 
 ## Resource Browser