feat: Horizontal scaling support to the Feast operator

Signed-off-by: ntkathole <nikhilkathole2683@gmail.com>
feast-dev · ntkathole · Feb 27, 2026 · Feb 21, 2026 · Feb 23, 2026 · Feb 26, 2026
commit 6656ec142d161529f2ceb21b06d7998963871df0
diff --git a/.secrets.baseline b/.secrets.baseline
@@ -90,6 +90,10 @@
     {
       "path": "detect_secrets.filters.allowlist.is_line_allowlisted"
     },
+    {
+      "path": "detect_secrets.filters.common.is_baseline_file",
+      "filename": ".secrets.baseline"
+    },
     {
       "path": "detect_secrets.filters.common.is_ignored_due_to_verification_policies",
       "min_level": 2
@@ -930,7 +934,7 @@
         "filename": "infra/feast-operator/api/v1/featurestore_types.go",
         "hashed_secret": "44e17306b837162269a410204daaa5ecee4ec22c",
         "is_verified": false,
-        "line_number": 657
+        "line_number": 692
       }
     ],
     "infra/feast-operator/api/v1/zz_generated.deepcopy.go": [
@@ -939,21 +943,21 @@
         "filename": "infra/feast-operator/api/v1/zz_generated.deepcopy.go",
         "hashed_secret": "f914fc9324de1bec1ad13dec94a8ea2ddb41fc87",
         "is_verified": false,
-        "line_number": 615
+        "line_number": 658
       },
       {
         "type": "Secret Keyword",
         "filename": "infra/feast-operator/api/v1/zz_generated.deepcopy.go",
         "hashed_secret": "44e17306b837162269a410204daaa5ecee4ec22c",
         "is_verified": false,
-        "line_number": 1123
+        "line_number": 1206
       },
       {
         "type": "Secret Keyword",
         "filename": "infra/feast-operator/api/v1/zz_generated.deepcopy.go",
         "hashed_secret": "c2028031c154bbe86fd69bef740855c74b927dcf",
         "is_verified": false,
-        "line_number": 1128
+        "line_number": 1211
       }
     ],
     "infra/feast-operator/api/v1alpha1/featurestore_types.go": [
@@ -1152,7 +1156,7 @@
         "filename": "infra/feast-operator/internal/controller/services/services.go",
         "hashed_secret": "36dc326eb15c7bdd8d91a6b87905bcea20b637d1",
         "is_verified": false,
-        "line_number": 164
+        "line_number": 178
       }
     ],
     "infra/feast-operator/internal/controller/services/tls_test.go": [
@@ -1535,5 +1539,5 @@
       }
     ]
   },
-  "generated_at": "2026-02-19T06:53:49Z"
+  "generated_at": "2026-02-21T16:33:24Z"
 }
@@ -65,7 +65,9 @@ spec:
 > _More advanced FeatureStore CR examples can be found in the feast-operator [samples directory](../../infra/feast-operator/config/samples)._
 
 {% hint style="success" %}
-Important note: Scaling a Feature Store Deployment should only be done if the configured data store(s) will support it.
+**Scaling:** The Feast Operator supports horizontal scaling via static replicas, HPA autoscaling, or external autoscalers like [KEDA](https://keda.sh). Scaling requires DB-backed persistence for all enabled services.
 
-Please check the how-to guide for some specific recommendations on [how to scale Feast](./scaling-feast.md).
+See the [Horizontal Scaling with the Feast Operator](./scaling-feast.md#horizontal-scaling-with-the-feast-operator) guide for configuration details, or check the general recommendations on [how to scale Feast](./scaling-feast.md).
 {% endhint %}
+
+> _Sample scaling CRs are available at [`v1_featurestore_scaling_static.yaml`](../../infra/feast-operator/config/samples/v1_featurestore_scaling_static.yaml) and [`v1_featurestore_scaling_hpa.yaml`](../../infra/feast-operator/config/samples/v1_featurestore_scaling_hpa.yaml)._
@@ -23,4 +23,157 @@ However, this process does not scale for large data sets, since it's executed on
 Feast supports pluggable [Compute Engines](../getting-started/components/compute-engine.md), that allow the materialization process to be scaled up.
 Aside from the local process, Feast supports a [Lambda-based materialization engine](https://rtd.feast.dev/en/master/#alpha-lambda-based-engine), and a [Bytewax-based materialization engine](https://rtd.feast.dev/en/master/#bytewax-engine).
 
-Users may also be able to build an engine to scale up materialization using existing infrastructure in their organizations.
+Users may also be able to build an engine to scale up materialization using existing infrastructure in their organizations.
+
+### Horizontal Scaling with the Feast Operator
+
+When running Feast on Kubernetes with the [Feast Operator](./feast-on-kubernetes.md), you can horizontally scale the FeatureStore deployment by adding a `scaling` field to the `services` section of the FeatureStore CR.
+
+**Prerequisites:** Horizontal scaling requires **DB-backed persistence** for all enabled services (online store, offline store, and registry). File-based persistence (SQLite, DuckDB, `registry.db`) is incompatible with multiple replicas because these backends do not support concurrent access from multiple pods.
+
+#### Static Replicas
+
+Set a fixed number of replicas:
+
+```yaml
+apiVersion: feast.dev/v1
+kind: FeatureStore
+metadata:
+  name: sample-scaling
+spec:
+  feastProject: my_project
+  services:
+    scaling:
+      replicas: 3
+    onlineStore:
+      persistence:
+        store:
+          type: postgres
+          secretRef:
+            name: feast-data-stores
+    registry:
+      local:
+        persistence:
+          store:
+            type: sql
+            secretRef:
+              name: feast-data-stores
+```
+
+#### Autoscaling with HPA
+
+Configure a HorizontalPodAutoscaler to dynamically scale based on metrics:
+
+```yaml
+apiVersion: feast.dev/v1
+kind: FeatureStore
+metadata:
+  name: sample-autoscaling
+spec:
+  feastProject: my_project
+  services:
+    scaling:
+      autoscaling:
+        minReplicas: 2
+        maxReplicas: 10
+        metrics:
+        - type: Resource
+          resource:
+            name: cpu
+            target:
+              type: Utilization
+              averageUtilization: 70
+    onlineStore:
+      persistence:
+        store:
+          type: postgres
+          secretRef:
+            name: feast-data-stores
+      server:
+        resources:
+          requests:
+            cpu: 200m
+            memory: 256Mi
+    registry:
+      local:
+        persistence:
+          store:
+            type: sql
+            secretRef:
+              name: feast-data-stores
+```
+
+{% hint style="info" %}
+When autoscaling is configured, the operator automatically sets the deployment strategy to `RollingUpdate` (instead of the default `Recreate`) to ensure zero-downtime scaling. You can override this by explicitly setting `deploymentStrategy` in the CR.
+{% endhint %}
+
+#### Validation Rules
+
+The operator enforces the following rules:
+- `replicas` and `autoscaling` are **mutually exclusive** -- you cannot set both.
+- Scaling with `replicas > 1` or any `autoscaling` config is **rejected** if any enabled service uses file-based persistence.
+- S3 (`s3://`) and GCS (`gs://`) backed registry file persistence is allowed with scaling, since these object stores support concurrent readers.
+
+#### Using KEDA (Kubernetes Event-Driven Autoscaling)
+
+[KEDA](https://keda.sh) is also supported as an external autoscaler. Rather than using the built-in `autoscaling` field, you can create a KEDA `ScaledObject` that targets the Feast deployment directly.
+
+When using KEDA, do **not** set the `scaling.autoscaling` field -- KEDA manages its own HPA. The operator will preserve the replica count set by KEDA since it does not override externally managed replicas.
+
+There are a few things you must configure manually when using KEDA:
+
+1. **Set the deployment strategy to `RollingUpdate`** -- The operator defaults to `Recreate` when no `scaling` config is present, which causes downtime on scale events. Override it explicitly:
+
+```yaml
+apiVersion: feast.dev/v1
+kind: FeatureStore
+metadata:
+  name: sample-keda
+spec:
+  feastProject: my_project
+  services:
+    deploymentStrategy:
+      type: RollingUpdate
+    onlineStore:
+      persistence:
+        store:
+          type: postgres
+          secretRef:
+            name: feast-data-stores
+    registry:
+      local:
+        persistence:
+          store:
+            type: sql
+            secretRef:
+              name: feast-data-stores
+```
+
+2. **Ensure DB-backed persistence** -- The operator's persistence validation only applies when the built-in `scaling` field is used. With KEDA, you are responsible for ensuring all enabled services use DB-backed persistence (not SQLite, DuckDB, or local `registry.db`).
+
+3. **Create a KEDA `ScaledObject`** targeting the Feast deployment:
+
+```yaml
+apiVersion: keda.sh/v1alpha1
+kind: ScaledObject
+metadata:
+  name: feast-scaledobject
+spec:
+  scaleTargetRef:
+    name: feast-sample-keda   # must match the Feast deployment name
+  minReplicaCount: 2
+  maxReplicaCount: 10
+  triggers:
+  - type: prometheus
+    metadata:
+      serverAddress: http://prometheus.monitoring.svc:9090
+      metricName: http_requests_total
+      query: sum(rate(http_requests_total{service="feast"}[2m]))
+      threshold: "100"
+```
+
+{% hint style="warning" %}
+KEDA-created HPAs are not owned by the Feast operator. The operator will not interfere with them, but it also will not clean them up if the FeatureStore CR is deleted. You must manage the KEDA `ScaledObject` lifecycle independently.
+{% endhint %}
+
+For the full API reference, see the [FeatureStore CRD reference](../../infra/feast-operator/docs/api/markdown/ref.md).
@@ -18,6 +18,7 @@ package v1
 
 import (
 	appsv1 "k8s.io/api/apps/v1"
+	autoscalingv2 "k8s.io/api/autoscaling/v2"
 	batchv1 "k8s.io/api/batch/v1"
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -301,6 +302,40 @@ type FeatureStoreServices struct {
 	DisableInitContainers bool `json:"disableInitContainers,omitempty"`
 	// Volumes specifies the volumes to mount in the FeatureStore deployment. A corresponding `VolumeMount` should be added to whichever feast service(s) require access to said volume(s).
 	Volumes []corev1.Volume `json:"volumes,omitempty"`
+	// Scaling configures horizontal scaling for the FeatureStore deployment.
+	// Requires DB-based persistence for all enabled services when replicas > 1 or autoscaling is configured.
+	Scaling *ScalingConfig `json:"scaling,omitempty"`
+}
+
+// ScalingConfig configures horizontal scaling for the FeatureStore deployment.
+// +kubebuilder:validation:XValidation:rule="!has(self.replicas) || !has(self.autoscaling)",message="replicas and autoscaling are mutually exclusive."
+type ScalingConfig struct {
+	// Replicas is the static number of pod replicas. Mutually exclusive with autoscaling.
+	// +kubebuilder:validation:Minimum=1
+	// +optional
+	Replicas *int32 `json:"replicas,omitempty"`
+	// Autoscaling configures a HorizontalPodAutoscaler for the FeatureStore deployment.
+	// Mutually exclusive with replicas.
+	// +optional
+	Autoscaling *AutoscalingConfig `json:"autoscaling,omitempty"`
+}
+
+// AutoscalingConfig defines HPA settings for the FeatureStore deployment.
+type AutoscalingConfig struct {
+	// MinReplicas is the lower limit for the number of replicas. Defaults to 1.
+	// +kubebuilder:validation:Minimum=1
+	// +optional
+	MinReplicas *int32 `json:"minReplicas,omitempty"`
+	// MaxReplicas is the upper limit for the number of replicas. Required.
+	// +kubebuilder:validation:Minimum=1
+	MaxReplicas int32 `json:"maxReplicas"`
+	// Metrics contains the specifications for which to use to calculate the desired replica count.
+	// If not set, defaults to 80% CPU utilization.
+	// +optional
+	Metrics []autoscalingv2.MetricSpec `json:"metrics,omitempty"`
+	// Behavior configures the scaling behavior of the target.
+	// +optional
+	Behavior *autoscalingv2.HorizontalPodAutoscalerBehavior `json:"behavior,omitempty"`
 }
 
 // OfflineStore configures the offline store service
@@ -690,6 +725,16 @@ type FeatureStoreStatus struct {
 	FeastVersion     string             `json:"feastVersion,omitempty"`
 	Phase            string             `json:"phase,omitempty"`
 	ServiceHostnames ServiceHostnames   `json:"serviceHostnames,omitempty"`
+	// ScalingStatus reports the current scaling state of the FeatureStore deployment.
+	ScalingStatus *ScalingStatus `json:"scalingStatus,omitempty"`
+}
+
+// ScalingStatus reports the observed scaling state.
+type ScalingStatus struct {
+	// CurrentReplicas is the current number of pod replicas.
+	CurrentReplicas int32 `json:"currentReplicas,omitempty"`
+	// DesiredReplicas is the desired number of pod replicas.
+	DesiredReplicas int32 `json:"desiredReplicas,omitempty"`
 }
 
 // ServiceHostnames defines the service hostnames in the format of <domain>:<port>, e.g. example.svc.cluster.local:80