diff --git a/src/pathcomp/backend/pathComp_tools.h b/src/pathcomp/backend/pathComp_tools.h
index 8fe704c3932c219e0f04046fcc62d6f1da5f9b66..adbbf30c4fda48564c126369b0aace839cdf5d93 100644
--- a/src/pathcomp/backend/pathComp_tools.h
+++ b/src/pathcomp/backend/pathComp_tools.h
@@ -121,7 +121,7 @@ struct map_nodes_t {
 };
 
 #define MAX_NUM_VERTICES				20 // 100 # LGR: reduced from 100 to 20 to divide by 5 the memory used
-#define MAX_NUM_EDGES					10 // 100 # LGR: reduced from 100 to 10 to divide by 10 the memory used
+#define MAX_NUM_EDGES					20 // 100 # LGR: reduced from 100 to 20 to divide by 5 the memory used
 // Structures for the graph composition
 struct targetNodes_t {
 	// remote / targeted node
diff --git a/src/pathcomp/frontend/service/PathCompServiceServicerImpl.py b/src/pathcomp/frontend/service/PathCompServiceServicerImpl.py
index 4f725cce749dbda2a7bebf56477bd6c8ee29b7ad..ca4132754fc4886704cb2984519ebc21a19bfd9c 100644
--- a/src/pathcomp/frontend/service/PathCompServiceServicerImpl.py
+++ b/src/pathcomp/frontend/service/PathCompServiceServicerImpl.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import grpc, logging
+import grpc, logging, threading
 from common.Constants import DEFAULT_CONTEXT_UUID, INTERDOMAIN_TOPOLOGY_UUID
 from common.method_wrappers.Decorator import MetricsPool, safe_and_metered_rpc_method
 from common.proto.context_pb2 import ContextId, Empty
@@ -35,11 +35,12 @@ ADMIN_CONTEXT_ID = ContextId(**json_context_id(DEFAULT_CONTEXT_UUID))
 class PathCompServiceServicerImpl(PathCompServiceServicer):
     def __init__(self) -> None:
         LOGGER.debug('Creating Servicer...')
+        self._lock = threading.Lock()
         LOGGER.debug('Servicer Created')
 
     @safe_and_metered_rpc_method(METRICS_POOL, LOGGER)
     def Compute(self, request : PathCompRequest, context : grpc.ServicerContext) -> PathCompReply:
-        LOGGER.info('[Compute] begin ; request = {:s}'.format(grpc_message_to_json_string(request)))
+        LOGGER.debug('[Compute] begin ; request = {:s}'.format(grpc_message_to_json_string(request)))
 
         context_client = ContextClient()
 
@@ -66,8 +67,10 @@ class PathCompServiceServicerImpl(PathCompServiceServicer):
         #import time
         #ts = time.time()
         #algorithm.execute('request-{:f}.json'.format(ts), 'reply-{:f}.json'.format(ts))
-        algorithm.execute()
+        with self._lock:
+            # ensure backend receives requests one at a time
+            algorithm.execute()
 
         reply = algorithm.get_reply()
-        LOGGER.info('[Compute] end ; reply = {:s}'.format(grpc_message_to_json_string(reply)))
+        LOGGER.debug('[Compute] end ; reply = {:s}'.format(grpc_message_to_json_string(reply)))
         return reply
diff --git a/src/pathcomp/frontend/service/algorithms/_Algorithm.py b/src/pathcomp/frontend/service/algorithms/_Algorithm.py
index 3833642457bc5f8c2ba7b7d09f384a87dfabe41d..a24ef769313c7d71d28e6bcc5526cbc398e05c08 100644
--- a/src/pathcomp/frontend/service/algorithms/_Algorithm.py
+++ b/src/pathcomp/frontend/service/algorithms/_Algorithm.py
@@ -93,22 +93,22 @@ class _Algorithm:
     def execute(self, dump_request_filename : Optional[str] = None, dump_reply_filename : Optional[str] = None) -> None:
         request = {'serviceList': self.service_list, 'deviceList': self.device_list, 'linkList': self.link_list}
 
-        self.logger.info('[execute] request={:s}'.format(str(request)))
+        self.logger.debug('[execute] request={:s}'.format(str(request)))
         if dump_request_filename is not None:
             with open(dump_request_filename, 'w', encoding='UTF-8') as f:
                 f.write(json.dumps(request, sort_keys=True, indent=4))
 
-        self.logger.info('[execute] BACKEND_URL: {:s}'.format(str(BACKEND_URL)))
+        self.logger.debug('[execute] BACKEND_URL: {:s}'.format(str(BACKEND_URL)))
         reply = requests.post(BACKEND_URL, json=request)
         self.status_code = reply.status_code
         self.raw_reply = reply.content.decode('UTF-8')
 
-        self.logger.info('[execute] status_code={:s} reply={:s}'.format(str(reply.status_code), str(self.raw_reply)))
+        self.logger.debug('[execute] status_code={:s} reply={:s}'.format(str(reply.status_code), str(self.raw_reply)))
         if dump_reply_filename is not None:
             with open(dump_reply_filename, 'w', encoding='UTF-8') as f:
                 f.write('status_code={:s} reply={:s}'.format(str(self.status_code), str(self.raw_reply)))
 
-        if reply.status_code not in {requests.codes.ok}:
+        if reply.status_code not in {requests.codes.ok}: # pylint: disable=no-member
             raise Exception('Backend error({:s}) for request({:s})'.format(
                 str(self.raw_reply), json.dumps(request, sort_keys=True)))