diff --git a/common/prefs.cc b/common/prefs.cc
index a4b97d0..12d06c0 100644
--- a/common/prefs.cc
+++ b/common/prefs.cc
@@ -29,31 +29,12 @@
 
 namespace chromeos_update_engine {
 
-bool Prefs::Init(const base::FilePath& prefs_dir) {
-  prefs_dir_ = prefs_dir;
-  return true;
+bool PrefsBase::GetString(const string& key, string* value) const {
+  return storage_->GetKey(key, value);
 }
 
-bool Prefs::GetString(const string& key, string* value) const {
-  base::FilePath filename;
-  TEST_AND_RETURN_FALSE(GetFileNameForKey(key, &filename));
-  if (!base::ReadFileToString(filename, value)) {
-    LOG(INFO) << key << " not present in " << prefs_dir_.value();
-    return false;
-  }
-  return true;
-}
-
-bool Prefs::SetString(const string& key, const string& value) {
-  base::FilePath filename;
-  TEST_AND_RETURN_FALSE(GetFileNameForKey(key, &filename));
-  if (!base::DirectoryExists(filename.DirName())) {
-    // Only attempt to create the directory if it doesn't exist to avoid calls
-    // to parent directories where we might not have permission to write to.
-    TEST_AND_RETURN_FALSE(base::CreateDirectory(filename.DirName()));
-  }
-  TEST_AND_RETURN_FALSE(base::WriteFile(filename, value.data(), value.size()) ==
-                        static_cast<int>(value.size()));
+bool PrefsBase::SetString(const string& key, const string& value) {
+  TEST_AND_RETURN_FALSE(storage_->SetKey(key, value));
   const auto observers_for_key = observers_.find(key);
   if (observers_for_key != observers_.end()) {
     std::vector<ObserverInterface*> copy_observers(observers_for_key->second);
@@ -63,7 +44,7 @@
   return true;
 }
 
-bool Prefs::GetInt64(const string& key, int64_t* value) const {
+bool PrefsBase::GetInt64(const string& key, int64_t* value) const {
   string str_value;
   if (!GetString(key, &str_value))
     return false;
@@ -72,11 +53,11 @@
   return true;
 }
 
-bool Prefs::SetInt64(const string& key, const int64_t value) {
+bool PrefsBase::SetInt64(const string& key, const int64_t value) {
   return SetString(key, base::Int64ToString(value));
 }
 
-bool Prefs::GetBoolean(const string& key, bool* value) const {
+bool PrefsBase::GetBoolean(const string& key, bool* value) const {
   string str_value;
   if (!GetString(key, &str_value))
     return false;
@@ -92,20 +73,16 @@
   return false;
 }
 
-bool Prefs::SetBoolean(const string& key, const bool value) {
+bool PrefsBase::SetBoolean(const string& key, const bool value) {
   return SetString(key, value ? "true" : "false");
 }
 
-bool Prefs::Exists(const string& key) const {
-  base::FilePath filename;
-  TEST_AND_RETURN_FALSE(GetFileNameForKey(key, &filename));
-  return base::PathExists(filename);
+bool PrefsBase::Exists(const string& key) const {
+  return storage_->KeyExists(key);
 }
 
-bool Prefs::Delete(const string& key) {
-  base::FilePath filename;
-  TEST_AND_RETURN_FALSE(GetFileNameForKey(key, &filename));
-  TEST_AND_RETURN_FALSE(base::DeleteFile(filename, false));
+bool PrefsBase::Delete(const string& key) {
+  TEST_AND_RETURN_FALSE(storage_->DeleteKey(key));
   const auto observers_for_key = observers_.find(key);
   if (observers_for_key != observers_.end()) {
     std::vector<ObserverInterface*> copy_observers(observers_for_key->second);
@@ -115,11 +92,11 @@
   return true;
 }
 
-void Prefs::AddObserver(const string& key, ObserverInterface* observer) {
+void PrefsBase::AddObserver(const string& key, ObserverInterface* observer) {
   observers_[key].push_back(observer);
 }
 
-void Prefs::RemoveObserver(const string& key, ObserverInterface* observer) {
+void PrefsBase::RemoveObserver(const string& key, ObserverInterface* observer) {
   std::vector<ObserverInterface*>& observers_for_key = observers_[key];
   auto observer_it =
       std::find(observers_for_key.begin(), observers_for_key.end(), observer);
@@ -127,8 +104,55 @@
     observers_for_key.erase(observer_it);
 }
 
-bool Prefs::GetFileNameForKey(const string& key,
-                              base::FilePath* filename) const {
+// Prefs
+
+bool Prefs::Init(const base::FilePath& prefs_dir) {
+  return file_storage_.Init(prefs_dir);
+}
+
+bool Prefs::FileStorage::Init(const base::FilePath& prefs_dir) {
+  prefs_dir_ = prefs_dir;
+  return true;
+}
+
+bool Prefs::FileStorage::GetKey(const string& key, string* value) const {
+  base::FilePath filename;
+  TEST_AND_RETURN_FALSE(GetFileNameForKey(key, &filename));
+  if (!base::ReadFileToString(filename, value)) {
+    LOG(INFO) << key << " not present in " << prefs_dir_.value();
+    return false;
+  }
+  return true;
+}
+
+bool Prefs::FileStorage::SetKey(const string& key, const string& value) {
+  base::FilePath filename;
+  TEST_AND_RETURN_FALSE(GetFileNameForKey(key, &filename));
+  if (!base::DirectoryExists(filename.DirName())) {
+    // Only attempt to create the directory if it doesn't exist to avoid calls
+    // to parent directories where we might not have permission to write to.
+    TEST_AND_RETURN_FALSE(base::CreateDirectory(filename.DirName()));
+  }
+  TEST_AND_RETURN_FALSE(base::WriteFile(filename, value.data(), value.size()) ==
+                        static_cast<int>(value.size()));
+  return true;
+}
+
+bool Prefs::FileStorage::KeyExists(const string& key) const {
+  base::FilePath filename;
+  TEST_AND_RETURN_FALSE(GetFileNameForKey(key, &filename));
+  return base::PathExists(filename);
+}
+
+bool Prefs::FileStorage::DeleteKey(const string& key) {
+  base::FilePath filename;
+  TEST_AND_RETURN_FALSE(GetFileNameForKey(key, &filename));
+  TEST_AND_RETURN_FALSE(base::DeleteFile(filename, false));
+  return true;
+}
+
+bool Prefs::FileStorage::GetFileNameForKey(const string& key,
+                                           base::FilePath* filename) const {
   // Allows only non-empty keys containing [A-Za-z0-9_-].
   TEST_AND_RETURN_FALSE(!key.empty());
   for (size_t i = 0; i < key.size(); ++i) {
@@ -140,4 +164,33 @@
   return true;
 }
 
+// MemoryPrefs
+
+bool MemoryPrefs::MemoryStorage::GetKey(const string& key,
+                                        string* value) const {
+  auto it = values_.find(key);
+  if (it == values_.end())
+    return false;
+  *value = it->second;
+  return true;
+}
+
+bool MemoryPrefs::MemoryStorage::SetKey(const string& key,
+                                        const string& value) {
+  values_[key] = value;
+  return true;
+}
+
+bool MemoryPrefs::MemoryStorage::KeyExists(const string& key) const {
+  return values_.find(key) != values_.end();
+}
+
+bool MemoryPrefs::MemoryStorage::DeleteKey(const string& key) {
+  auto it = values_.find(key);
+  if (it == values_.end())
+    return false;
+  values_.erase(it);
+  return true;
+}
+
 }  // namespace chromeos_update_engine