diff --git a/mantis-runtime/src/main/java/io/mantisrx/runtime/GroupToScalar.java b/mantis-runtime/src/main/java/io/mantisrx/runtime/GroupToScalar.java
index a3e35d064..cfb4cf35a 100644
--- a/mantis-runtime/src/main/java/io/mantisrx/runtime/GroupToScalar.java
+++ b/mantis-runtime/src/main/java/io/mantisrx/runtime/GroupToScalar.java
@@ -56,7 +56,7 @@ public class GroupToScalar<K, T, R> extends StageConfig<T, R> {
 
     GroupToScalar(GroupToScalarComputation<K, T, R> computation,
                   Config<K, T, R> config, Codec<K> inputKeyCodec, Codec<T> inputCodec) {
-        super(config.description, inputKeyCodec, inputCodec, config.codec, config.inputStrategy, config.parameters);
+        super(config.description, inputKeyCodec, inputCodec, config.codec, config.inputStrategy, config.parameters, config.concurrency);
         this.computation = computation;
         this.keyExpireTimeSeconds = config.keyExpireTimeSeconds;
     }
@@ -78,6 +78,7 @@ public static class Config<K, T, R> {
         // 'stateful group calculation' use case
         // do not allow config override
         private INPUT_STRATEGY inputStrategy = INPUT_STRATEGY.SERIAL;
+        private int concurrency = DEFAULT_STAGE_CONCURRENCY;
         private List<ParameterDefinition<?>> parameters = Collections.emptyList();
 
         /**
@@ -119,6 +120,12 @@ public Config<K, T, R> concurrentInput() {
             return this;
         }
 
+        public Config<K, T, R> concurrentInput(final int concurrency) {
+            this.inputStrategy = INPUT_STRATEGY.CONCURRENT;
+			this.concurrency = concurrency;
+            return this;
+        }
+
         public Codec<R> getCodec() {
             return codec;
         }
@@ -135,6 +142,8 @@ public INPUT_STRATEGY getInputStrategy() {
             return inputStrategy;
         }
 
+        public int getConcurrency() { return concurrency; }
+
         public Config<K, T, R> withParameters(List<ParameterDefinition<?>> params) {
             this.parameters = params;
             return this;
diff --git a/mantis-runtime/src/main/java/io/mantisrx/runtime/KeyValueStageConfig.java b/mantis-runtime/src/main/java/io/mantisrx/runtime/KeyValueStageConfig.java
index 5385cbe51..756639400 100644
--- a/mantis-runtime/src/main/java/io/mantisrx/runtime/KeyValueStageConfig.java
+++ b/mantis-runtime/src/main/java/io/mantisrx/runtime/KeyValueStageConfig.java
@@ -33,7 +33,12 @@ public abstract class KeyValueStageConfig<T, K, R> extends StageConfig<T, R> {
     private final Codec<K> keyCodec;
 
     public KeyValueStageConfig(String description, Codec<?> inputKeyCodec, Codec<T> inputCodec, Codec<K> outputKeyCodec, Codec<R> outputCodec, INPUT_STRATEGY inputStrategy, List<ParameterDefinition<?>> params) {
-        super(description, inputKeyCodec, inputCodec, outputCodec, inputStrategy, params);
+        super(description, inputKeyCodec, inputCodec, outputCodec, inputStrategy, params, DEFAULT_STAGE_CONCURRENCY);
+        this.keyCodec = outputKeyCodec;
+    }
+
+    public KeyValueStageConfig(String description, Codec<?> inputKeyCodec, Codec<T> inputCodec, Codec<K> outputKeyCodec, Codec<R> outputCodec, INPUT_STRATEGY inputStrategy, List<ParameterDefinition<?>> params, int concurrency) {
+        super(description, inputKeyCodec, inputCodec, outputCodec, inputStrategy, params, concurrency);
         this.keyCodec = outputKeyCodec;
     }
 
diff --git a/mantis-runtime/src/main/java/io/mantisrx/runtime/ScalarToGroup.java b/mantis-runtime/src/main/java/io/mantisrx/runtime/ScalarToGroup.java
index 54f1e71fc..7fb2a3206 100644
--- a/mantis-runtime/src/main/java/io/mantisrx/runtime/ScalarToGroup.java
+++ b/mantis-runtime/src/main/java/io/mantisrx/runtime/ScalarToGroup.java
@@ -54,7 +54,7 @@ public class ScalarToGroup<T, K, R> extends KeyValueStageConfig<T, K, R> {
 
     public ScalarToGroup(ToGroupComputation<T, K, R> computation,
                   Config<T, K, R> config, Codec<T> inputCodec) {
-        super(config.description, null, inputCodec, config.keyCodec, config.codec, config.inputStrategy, config.parameters);
+        super(config.description, null, inputCodec, config.keyCodec, config.codec, config.inputStrategy, config.parameters, config.concurrency);
         this.computation = computation;
         this.keyExpireTimeSeconds = config.keyExpireTimeSeconds;
 
@@ -76,6 +76,7 @@ public static class Config<T, K, R> {
         private String description;
         // default input type is concurrent for 'grouping' use case
         private INPUT_STRATEGY inputStrategy = INPUT_STRATEGY.CONCURRENT;
+        private int concurrency = DEFAULT_STAGE_CONCURRENCY;
         private long keyExpireTimeSeconds = Long.MAX_VALUE; // never expire by default
         private List<ParameterDefinition<?>> parameters = Collections.emptyList();
 
@@ -108,6 +109,7 @@ public Config<T, K, R> keyExpireTimeSeconds(long seconds) {
 
         public Config<T, K, R> serialInput() {
             this.inputStrategy = INPUT_STRATEGY.SERIAL;
+            this.concurrency = 1;
             return this;
         }
 
@@ -116,6 +118,12 @@ public Config<T, K, R> concurrentInput() {
             return this;
         }
 
+        public Config<T, K, R> concurrentInput(final int concurrency) {
+            this.inputStrategy = INPUT_STRATEGY.CONCURRENT;
+			this.concurrency = concurrency;
+            return this;
+        }
+
         public Config<T, K, R> description(String description) {
             this.description = description;
             return this;
@@ -137,6 +145,8 @@ public INPUT_STRATEGY getInputStrategy() {
             return inputStrategy;
         }
 
+        public int getConcurrency() { return concurrency; }
+
         public long getKeyExpireTimeSeconds() {
             return keyExpireTimeSeconds;
         }