diff --git a/buildbot_nix/__init__.py b/buildbot_nix/__init__.py
index 07543f3..f1f9731 100644
--- a/buildbot_nix/__init__.py
+++ b/buildbot_nix/__init__.py
@@ -64,11 +64,15 @@ class NixBuilder:
     def to_nix_store(self):
         fullConnection = f"{self.sshUser}@{self.hostName}" if self.sshUser is not None else self.hostName
         fullConnection = f"{self.protocol}://{fullConnection}"
+        params = []
         if self.sshKey is not None:
-            fullConnection += f"?ssh-key={self.sshKey}"
+            params += f"ssh-key={self.sshKey}"
         if self.publicHostKey is not None:
             encoded_public_key = base64.b64encode(self.publicHostKey.encode('ascii')).decode('ascii')
-            fullConnection += f"?base64-ssh-public-host-key={encoded_public_key}"
+            params += f"base64-ssh-public-host-key={encoded_public_key}"
+        if params != []:
+            fullConnection += "?"
+            fullConnection += "&".join(params)
 
         return fullConnection
 
@@ -629,22 +633,10 @@ def nix_build_config(
 ) -> util.BuilderConfig:
     """Builds one nix flake attribute."""
     factory = util.BuildFactory()
-    factory.addStep(
-        steps.ShellCommand(
-            name="Copy the derivation to the local worker store",
-            command=[
-                "nix",
-                "copy",
-                "--derivation",
-                "--to",
-                "../store",
-                util.Interpolate("%(prop:drv_path)s^*")
-            ]
-        )
-    )
 
     # pick a store to run the build on
-    build_store = random.choice(build_stores)
+    # TODO proper scheduling instead of picking the first builder
+    build_store = build_stores[0]
 
     factory.addStep(
         NixBuildCommand(
@@ -657,8 +649,6 @@ def nix_build_config(
                 "--option",
                 "keep-going",
                 "true",
-                # do not build directly on the coordinator
-                "--max-jobs", "0",
                 "--option",
                 # stop stuck builds after 20 minutes
                 "--max-silent-time",