diff --git a/bibigrid/core/actions/create.py b/bibigrid/core/actions/create.py
index e4e6896d..306bdc5b 100644
--- a/bibigrid/core/actions/create.py
+++ b/bibigrid/core/actions/create.py
@@ -484,7 +484,7 @@ def start_start_server_threads(self):
             start_server_threads.append(start_server_thread)
             for worker in configuration.get("workerInstances", []):
                 if not worker.get("onDemand", True):
-                    for _ in range(int(worker["count"])):
+                    for _ in range(int(worker.get("count", 1))):
                         start_server_thread = return_threading.ReturnThread(target=self.start_worker,
                                                                             args=[worker, worker_count, configuration,
                                                                                   provider])
@@ -492,7 +492,7 @@ def start_start_server_threads(self):
                         start_server_threads.append(start_server_thread)
                         worker_count += 1
                 else:
-                    worker_count += worker["count"]
+                    worker_count += worker.get("count", 1)
         for start_server_thread in start_server_threads:
             start_server_thread.join()
 
diff --git a/bibigrid/core/rest/models.py b/bibigrid/core/rest/models.py
index 7a4fe108..ad7a59f6 100644
--- a/bibigrid/core/rest/models.py
+++ b/bibigrid/core/rest/models.py
@@ -11,35 +11,35 @@ class Role(BaseModel):
 class UserRole(BaseModel):
     hosts: List[str]
     roles: List[Role]
-    varsFiles: Optional[List[str]]
+    varsFiles: Optional[List[str]] = Field(default=[])
 
 class CloudScheduling(BaseModel):
     sshTimeout: Optional[int] = 5
 
 class BootVolume(BaseModel):
-    name: Optional[str]
+    name: Optional[str] = None
     terminate: Optional[bool] = True
     size: Optional[int] = 50
 
 class Volume(BaseModel):
-    name: Optional[str]
-    snapshot: Optional[str]
+    name: Optional[str] = None
+    snapshot: Optional[str] = None
     permanent: Optional[bool] = False
     semiPermanent: Optional[bool] = False
     exists: Optional[bool] = False
-    mountPoint: Optional[str]
+    mountPoint: Optional[str] = None
     size: Optional[int] = 50
-    fstype: Optional[str]
-    type: Optional[str]
+    fstype: Optional[str] = None
+    type: Optional[str] = None
 
 class Instance(BaseModel):
     type: str
     image: str
     onDemand: Optional[bool] = True
-    partitions: Optional[List[str]]
-    features: Optional[List[str]]
-    bootVolume: Optional[BootVolume]
-    volumes: Optional[List[Volume]]
+    partitions: Optional[List[str]] = Field(default=[])
+    features: Optional[List[str]] = Field(default=[])
+    bootVolume: Optional[BootVolume] = None
+    volumes: Optional[List[Volume]] = Field(default=[])
 
 class ElasticScheduling(BaseModel):
     SuspendTime: Optional[int] = 1800
@@ -48,11 +48,11 @@ class ElasticScheduling(BaseModel):
     TreeWidth: Optional[int] = 128
 
 class SlurmConf(BaseModel):
-    db: Optional[str]
-    db_user: Optional[str]
-    db_password: Optional[str]
-    munge_key: Optional[str]
-    elastic_scheduling: Optional[ElasticScheduling]
+    db: Optional[str] = "slurm"
+    db_user: Optional[str] = "slurm"
+    db_password: Optional[str] = "changeme"
+    munge_key: Optional[str] = None
+    elastic_scheduling: Optional[ElasticScheduling] = None
 
 class Gateway(BaseModel):
     ip: str
@@ -64,29 +64,29 @@ class MasterConfig(BaseModel):
     sshUser: str
     subnet: Optional[str] = Field(default=None)
     network: Optional[str] = Field(default=None)
-    cloud_identifier: str
-    sshPublicKeyFiles: Optional[List[str]]
+    cloud_identifier: Optional[str] = None
+    sshPublicKeyFiles: Optional[List[str]] = Field(default=[])
     sshTimeout: Optional[int] = 5
-    cloudScheduling: Optional[CloudScheduling]
-    nfsShares: Optional[List[str]]
-    userRoles: Optional[List[UserRole]]
+    cloudScheduling: Optional[CloudScheduling] = None
+    nfsShares: Optional[List[str]] = Field(default=[])
+    userRoles: Optional[List[UserRole]] = Field(default=[])
     localFS: Optional[bool] = False
     localDNSlookup: Optional[bool] = False
     slurm: Optional[bool] = True
-    slurmConf: Optional[SlurmConf]
+    slurmConf: Optional[SlurmConf] = None
     zabbix: Optional[bool] = False
     nfs: Optional[bool] = False
     ide: Optional[bool] = False
     useMasterAsCompute: Optional[bool] = True
     useMasterWithPublicIp: Optional[bool] = True
-    waitForServices: Optional[List[str]]
-    gateway: Optional[Gateway]
+    waitForServices: Optional[List[str]] = Field(default=[])
+    gateway: Optional[Gateway] = None
     dontUploadCredentials: Optional[bool] = False
     fallbackOnOtherImage: Optional[bool] = False
-    features: Optional[List[str]]
+    features: Optional[List[str]] = Field(default=[])
     workerInstances: List[Instance]
     masterInstance: Instance
-    bootVolume: Optional[BootVolume]
+    bootVolume: Optional[BootVolume] = None
 
 class OtherConfig(BaseModel):
     infrastructure: str
@@ -94,12 +94,12 @@ class OtherConfig(BaseModel):
     sshUser: str
     subnet: Optional[str] = Field(default=None)
     network: Optional[str] = Field(default=None)
-    cloud_identifier: str
-    waitForServices: Optional[List[str]]
-    features: Optional[List[str]]
+    cloud_identifier: Optional[str] = None
+    waitForServices: Optional[List[str]] = Field(default=[])
+    features: Optional[List[str]] = Field(default=[])
     workerInstances: List[Instance]
     vpnInstance: Instance
-    bootVolume: Optional[BootVolume]
+    bootVolume: Optional[BootVolume] = None
 
 class ConfigurationsModel(BaseModel):
     configurations: List[Union[MasterConfig, OtherConfig]]
diff --git a/bibigrid/core/startup_rest.py b/bibigrid/core/startup_rest.py
index d0678a93..d8a3372b 100644
--- a/bibigrid/core/startup_rest.py
+++ b/bibigrid/core/startup_rest.py
@@ -150,7 +150,7 @@ async def create_async():
         creator.create()
 
     try:
-        configurations = configurations_json.model_dump()
+        configurations = configurations_json.model_dump(exclude_none=True)["configurations"]
         providers = provider_handler.get_providers(configurations, log)
         creator = create.Create(providers=providers, configurations=configurations, log=log,
                                 config_path=None, cluster_id=cluster_id)