diff --git a/backend/Gemfile b/backend/Gemfile
index 95ef82e6..53a29fe3 100644
--- a/backend/Gemfile
+++ b/backend/Gemfile
@@ -13,7 +13,7 @@ gem "rake"
 gem "active_model_serializers", "0.9.8"
 
 # Use postgresql and mongo as the database for Active Record
-gem "mongoid", "7.3.3"
+gem "mongoid", "9.0.0"
 gem "pg"
 
 # Use Puma as the app server
diff --git a/backend/Gemfile.lock b/backend/Gemfile.lock
index 018d4ad6..eccee0a2 100644
--- a/backend/Gemfile.lock
+++ b/backend/Gemfile.lock
@@ -86,7 +86,7 @@ GEM
     bigdecimal (3.1.7)
     brakeman (6.1.2)
       racc
-    bson (4.15.0)
+    bson (5.0.0)
     bugsnag (6.26.0)
       concurrent-ruby (~> 1.0)
     builder (3.2.4)
@@ -231,12 +231,12 @@ GEM
     mini_mime (1.1.5)
     mini_portile2 (2.8.5)
     minitest (5.22.3)
-    mongo (2.19.3)
-      bson (>= 4.14.1, < 5.0.0)
-    mongoid (7.3.3)
-      activemodel (>= 5.1, < 6.2)
-      mongo (>= 2.10.5, < 3.0.0)
-      ruby2_keywords (~> 0.0.5)
+    mongo (2.20.0)
+      bson (>= 4.14.1, < 6.0.0)
+    mongoid (9.0.0)
+      activemodel (>= 5.1, < 7.2, != 7.0.0)
+      concurrent-ruby (>= 1.0.5, < 2.0)
+      mongo (>= 2.18.0, < 3.0.0)
     mongoid-compatibility (0.6.0)
       activesupport
       mongoid (>= 2.0)
@@ -490,7 +490,7 @@ DEPENDENCIES
   kaminari-actionview
   kaminari-mongoid
   letter_opener
-  mongoid (= 7.3.3)
+  mongoid (= 9.0.0)
   mongoid-rspec
   nearest_time_zone
   omniauth (= 1.8.1)