diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
index fc98a969d14..4d0b35007fa 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
@@ -256,6 +256,9 @@ public class DefaultCodegen implements CodegenConfig {
     // A cache to efficiently lookup a Schema instance based on the return value of `toModelName()`.
     private Map<String, Schema> modelNameToSchemaCache;
 
+    // A cache to efficiently lookup schema `toModelName()` based on the schema Key
+    private Map<String, String> schemaKeyToModelNameCache = new HashMap<>();
+
     @Override
     public List<CliOption> cliOptions() {
         return cliOptions;
@@ -2322,7 +2325,13 @@ public class DefaultCodegen implements CodegenConfig {
      */
     @Override
     public String toModelName(final String name) {
-        return camelize(modelNamePrefix + "_" + name + "_" + modelNameSuffix);
+        if (schemaKeyToModelNameCache.containsKey(name)) {
+            return schemaKeyToModelNameCache.get(name);
+        }
+
+        String camelizedName = camelize(modelNamePrefix + "_" + name + "_" + modelNameSuffix);
+        schemaKeyToModelNameCache.put(name, camelizedName);
+        return camelizedName;
     }
 
     private static class NamedSchema {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
index fa09150e555..7093997f0b9 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
@@ -90,6 +90,9 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
     // special property keywords not allowed as these are the function names in the model files
     protected Set<String> propertySpecialKeywords = new HashSet<>(Arrays.asList("ToString", "ToJson", "GetHashCode", "Equals", "ShouldSerializeToString"));
 
+    // A cache to efficiently lookup schema `toModelName()` based on the schema Key
+    private Map<String, String> schemaKeyToModelNameCache = new HashMap<>();
+
     public AbstractCSharpCodegen() {
         super();
 
@@ -1035,6 +1038,13 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
         if (importMapping.containsKey(name)) {
             return importMapping.get(name);
         }
+
+        // memoization
+        String origName = name;
+        if (schemaKeyToModelNameCache.containsKey(origName)) {
+            return schemaKeyToModelNameCache.get(origName);
+        }
+
         if (!StringUtils.isEmpty(modelNamePrefix)) {
             name = modelNamePrefix + "_" + name;
         }
@@ -1058,9 +1068,12 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
         }
 
+        String camelizedName = camelize(name);
+        schemaKeyToModelNameCache.put(origName, camelizedName);
+
         // camelize the model name
         // phone_number => PhoneNumber
-        return camelize(name);
+        return camelizedName;
     }
 
     @Override
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientCodegen.java
index 11861b57924..60c0d9117db 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientCodegen.java
@@ -49,6 +49,9 @@ public class GoClientCodegen extends AbstractGoCodegen {
     protected boolean isGoSubmodule = false;
     protected boolean useOneOfDiscriminatorLookup = false; // use oneOf discriminator's mapping for model lookup
 
+    // A cache to efficiently lookup schema `toModelName()` based on the schema Key
+    private Map<String, String> schemaKeyToModelNameCache = new HashMap<>();
+
     public GoClientCodegen() {
         super();
 
@@ -312,8 +315,14 @@ public class GoClientCodegen extends AbstractGoCodegen {
 
     @Override
     public String toModelName(String name) {
+        if (schemaKeyToModelNameCache.containsKey(name)) {
+            return schemaKeyToModelNameCache.get(name);
+        }
+
         // underscoring would also lowercase the whole name, thus losing acronyms which are in capitals
-        return camelize(toModel(name, false));
+        String camelizedName = camelize(toModel(name, false));
+        schemaKeyToModelNameCache.put(name, camelizedName);
+        return camelizedName;
     }
 
     public String escapeReservedWord(String name) {