diff --git a/include/connection_cache.hpp b/include/connection_cache.hpp
index a999232..5ed4e2d 100644
--- a/include/connection_cache.hpp
+++ b/include/connection_cache.hpp
@@ -6,6 +6,7 @@
 #include <boost/uuid/uuid.hpp>
 #include <memory>
 #include <map>
+#include <shared_mutex>
 
 namespace TrRouting {
 
@@ -46,6 +47,7 @@ class ScenarioConnectionCacheOne : public ScenarioConnectionCache {
     virtual void set(boost::uuids::uuid uuid, std::shared_ptr<ConnectionSet> cache);
 
   private:
+  mutable std::shared_mutex mutex; //Reader/Writer locking
     std::optional<boost::uuids::uuid> lastUuid;
     std::shared_ptr<ConnectionSet> lastConnection;
 };
@@ -68,6 +70,7 @@ class ScenarioConnectionCacheAll : public ScenarioConnectionCache {
     virtual void set(boost::uuids::uuid uuid, std::shared_ptr<ConnectionSet> cache);
 
   private:
+    mutable std::shared_mutex mutex; //Reader/Writer locking
     std::map<boost::uuids::uuid, std::shared_ptr<ConnectionSet> > connectionSets;
 };
 
diff --git a/src/connection_cache.cpp b/src/connection_cache.cpp
index a06ab06..87c9959 100644
--- a/src/connection_cache.cpp
+++ b/src/connection_cache.cpp
@@ -8,6 +8,7 @@
 namespace TrRouting {
   // ScenarioConnectionCacheOne
   std::optional<std::shared_ptr<ConnectionSet>> ScenarioConnectionCacheOne::get(boost::uuids::uuid uuid) const {
+    std::shared_lock lock(mutex); //Sharing lock when reading
     if (uuid == lastUuid) {
       return std::optional(lastConnection);
     } else {
@@ -16,12 +17,14 @@ namespace TrRouting {
   }
 
   void ScenarioConnectionCacheOne::set(boost::uuids::uuid uuid, std::shared_ptr<ConnectionSet> cache) {
+    std::unique_lock lock(mutex); //Exclusive lock when writing
     lastUuid = uuid;
     lastConnection = cache;
   }
 
   // ScenarioConnectionCacheAll
   std::optional<std::shared_ptr<ConnectionSet>> ScenarioConnectionCacheAll::get(boost::uuids::uuid uuid) const {
+    std::shared_lock lock(mutex); //Sharing lock when reading
     // Lookup the scenario uuid in the map. If found, returns it, if not, return a null_opt
     auto connectionSetItr = connectionSets.find(uuid);
     if (connectionSetItr != connectionSets.end()) {
@@ -33,7 +36,7 @@ namespace TrRouting {
 
   void ScenarioConnectionCacheAll::set(boost::uuids::uuid uuid, std::shared_ptr<ConnectionSet> cache) {
     spdlog::debug("Caching connection set for scenario {}", boost::uuids::to_string(uuid));
-
+    std::unique_lock lock(mutex); //Exclusive lock when writing
     connectionSets[uuid] = cache;
   }
 }