diff --git a/src/ray/common/client_connection.cc b/src/ray/common/client_connection.cc
index dde14d680..21588177a 100644
--- a/src/ray/common/client_connection.cc
+++ b/src/ray/common/client_connection.cc
@@ -206,7 +206,7 @@ ClientConnection<T>::ClientConnection(MessageHandler<T> &message_handler,
       error_message_type_(error_message_type) {}
 
 template <class T>
-const ClientID &ClientConnection<T>::GetClientId() {
+const ClientID &ClientConnection<T>::GetClientId() const {
   return client_id_;
 }
 
diff --git a/src/ray/common/client_connection.h b/src/ray/common/client_connection.h
index 2aee25681..28bdad5b5 100644
--- a/src/ray/common/client_connection.h
+++ b/src/ray/common/client_connection.h
@@ -156,7 +156,7 @@ class ClientConnection : public ServerConnection<T> {
   }
 
   /// \return The ClientID of the remote client.
-  const ClientID &GetClientId();
+  const ClientID &GetClientId() const;
 
   /// \param client_id The ClientID of the remote client.
   void SetClientID(const ClientID &client_id);
diff --git a/src/ray/raylet/scheduling_resources.h b/src/ray/raylet/scheduling_resources.h
index 80b2abea6..daf6372c4 100644
--- a/src/ray/raylet/scheduling_resources.h
+++ b/src/ray/raylet/scheduling_resources.h
@@ -145,17 +145,17 @@ class ResourceIds {
   ///
   /// \param resource_quantity: The total amount of resource. This must either be
   /// a whole number or a fraction less than 1.
-  ResourceIds(double resource_quantity);
+  explicit ResourceIds(double resource_quantity);
 
   /// \brief Constructs ResourceIds with a given set of whole IDs.
   ///
   /// \param whole_ids: A vector of the resource IDs that are completely available.
-  ResourceIds(const std::vector<int64_t> &whole_ids);
+  explicit ResourceIds(const std::vector<int64_t> &whole_ids);
 
   /// \brief Constructs ResourceIds with a given set of fractional IDs.
   ///
   /// \param fractional_ids: A vector of the resource IDs that are partially available.
-  ResourceIds(const std::vector<std::pair<int64_t, double>> &fractional_ids);
+  explicit ResourceIds(const std::vector<std::pair<int64_t, double>> &fractional_ids);
 
   /// \brief Constructs ResourceIds with a given set of whole IDs and fractional IDs.
   ///
diff --git a/src/ray/raylet/worker_pool.cc b/src/ray/raylet/worker_pool.cc
index daf928f98..41e056e51 100644
--- a/src/ray/raylet/worker_pool.cc
+++ b/src/ray/raylet/worker_pool.cc
@@ -144,7 +144,7 @@ void WorkerPool::StartWorkerProcess(const Language &language) {
                  << strerror(errno);
 }
 
-void WorkerPool::RegisterWorker(std::shared_ptr<Worker> worker) {
+void WorkerPool::RegisterWorker(const std::shared_ptr<Worker> &worker) {
   auto pid = worker->Pid();
   RAY_LOG(DEBUG) << "Registering worker with pid " << pid;
   auto &state = GetStateForLanguage(worker->GetLanguage());
@@ -158,7 +158,7 @@ void WorkerPool::RegisterWorker(std::shared_ptr<Worker> worker) {
   }
 }
 
-void WorkerPool::RegisterDriver(std::shared_ptr<Worker> driver) {
+void WorkerPool::RegisterDriver(const std::shared_ptr<Worker> &driver) {
   RAY_CHECK(!driver->GetAssignedTaskId().is_nil());
   auto &state = GetStateForLanguage(driver->GetLanguage());
   state.registered_drivers.insert(std::move(driver));
@@ -186,7 +186,7 @@ std::shared_ptr<Worker> WorkerPool::GetRegisteredDriver(
   return nullptr;
 }
 
-void WorkerPool::PushWorker(std::shared_ptr<Worker> worker) {
+void WorkerPool::PushWorker(const std::shared_ptr<Worker> &worker) {
   // Since the worker is now idle, unset its assigned task ID.
   RAY_CHECK(worker->GetAssignedTaskId().is_nil())
       << "Idle workers cannot have an assigned task ID";
@@ -218,13 +218,13 @@ std::shared_ptr<Worker> WorkerPool::PopWorker(const TaskSpecification &task_spec
   return worker;
 }
 
-bool WorkerPool::DisconnectWorker(std::shared_ptr<Worker> worker) {
+bool WorkerPool::DisconnectWorker(const std::shared_ptr<Worker> &worker) {
   auto &state = GetStateForLanguage(worker->GetLanguage());
   RAY_CHECK(RemoveWorker(state.registered_workers, worker));
   return RemoveWorker(state.idle, worker);
 }
 
-void WorkerPool::DisconnectDriver(std::shared_ptr<Worker> driver) {
+void WorkerPool::DisconnectDriver(const std::shared_ptr<Worker> &driver) {
   auto &state = GetStateForLanguage(driver->GetLanguage());
   RAY_CHECK(RemoveWorker(state.registered_drivers, driver));
 }
diff --git a/src/ray/raylet/worker_pool.h b/src/ray/raylet/worker_pool.h
index 50d7c8998..ab9ca04ef 100644
--- a/src/ray/raylet/worker_pool.h
+++ b/src/ray/raylet/worker_pool.h
@@ -57,12 +57,12 @@ class WorkerPool {
   /// pool after it becomes idle (e.g., requests a work assignment).
   ///
   /// \param The Worker to be registered.
-  void RegisterWorker(std::shared_ptr<Worker> worker);
+  void RegisterWorker(const std::shared_ptr<Worker> &worker);
 
   /// Register a new driver.
   ///
   /// \param The driver to be registered.
-  void RegisterDriver(const std::shared_ptr<Worker> worker);
+  void RegisterDriver(const std::shared_ptr<Worker> &worker);
 
   /// Get the client connection's registered worker.
   ///
@@ -84,17 +84,17 @@ class WorkerPool {
   ///
   /// \param The worker to disconnect. The worker must be registered.
   /// \return Whether the given worker was in the pool of idle workers.
-  bool DisconnectWorker(std::shared_ptr<Worker> worker);
+  bool DisconnectWorker(const std::shared_ptr<Worker> &worker);
 
   /// Disconnect a registered driver.
   ///
   /// \param The driver to disconnect. The driver must be registered.
-  void DisconnectDriver(std::shared_ptr<Worker> driver);
+  void DisconnectDriver(const std::shared_ptr<Worker> &driver);
 
   /// Add an idle worker to the pool.
   ///
   /// \param The idle worker to add.
-  void PushWorker(std::shared_ptr<Worker> worker);
+  void PushWorker(const std::shared_ptr<Worker> &worker);
 
   /// Pop an idle worker from the pool. The caller is responsible for pushing
   /// the worker back onto the pool once the worker has completed its work.