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diff --git a/src/mongo/db/free_mon/free_mon_storage.h b/src/mongo/db/free_mon/free_mon_storage.h
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+/**
+ *    Copyright (C) 2018-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <boost/optional.hpp>
+
+#include "mongo/bson/bsonobj.h"
+#include "mongo/db/free_mon/free_mon_storage_gen.h"
+#include "mongo/db/operation_context.h"
+
+namespace mongo {
+
+/**
+ * Storage tier for Free Monitoring. Provides access to storage engine.
+ */
+class FreeMonStorage {
+public:
+    /**
+     * The _id value in admin.system.version.
+     */
+    static constexpr auto kFreeMonDocIdKey = "free_monitoring"_sd;
+
+    /**
+     * Reads document from disk if it exists.
+     */
+    static boost::optional<FreeMonStorageState> read(OperationContext* opCtx);
+
+    /**
+     * Replaces document on disk with contents of document. Creates document if it does not exist.
+     */
+    static void replace(OperationContext* opCtx, const FreeMonStorageState& doc);
+
+    /**
+     * Deletes document on disk if it exists.
+     */
+    static void deleteState(OperationContext* opCtx);
+
+    /**
+     * Reads the singelton document from local.clustermanager.
+     *
+     * Returns nothing if there are more then one document or it does not exist.
+     */
+    static boost::optional<BSONObj> readClusterManagerState(OperationContext* opCtx);
+};
+
+}  // namespace mongo