diff --git a/changelogs/unreleased/index-members-user-id-source-id-source-type.yml b/changelogs/unreleased/index-members-user-id-source-id-source-type.yml
new file mode 100644
index 0000000000000000000000000000000000000000..9f3000facf6f64dc70ba63d87d8cc37dbaa49072
--- /dev/null
+++ b/changelogs/unreleased/index-members-user-id-source-id-source-type.yml
@@ -0,0 +1,5 @@
+---
+title: Add migration to index members on user_id, source_id, and source_type
+merge_request: 59051
+author:
+type: performance
diff --git a/db/post_migrate/20210409185501_index_members_on_user_id_source_id_source_type.rb b/db/post_migrate/20210409185501_index_members_on_user_id_source_id_source_type.rb
new file mode 100644
index 0000000000000000000000000000000000000000..d20eb5e4ea37ba93cd02927ecdc2e8c0c923010e
--- /dev/null
+++ b/db/post_migrate/20210409185501_index_members_on_user_id_source_id_source_type.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class IndexMembersOnUserIdSourceIdSourceType < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  INDEX_NAME = 'index_members_on_user_id_source_id_source_type'
+
+  def up
+    add_concurrent_index(:members, [:user_id, :source_id, :source_type], name: INDEX_NAME)
+  end
+
+  def down
+    remove_concurrent_index_by_name(:members, INDEX_NAME)
+  end
+end
diff --git a/db/post_migrate/20210409185531_remove_members_index_on_user_id.rb b/db/post_migrate/20210409185531_remove_members_index_on_user_id.rb
new file mode 100644
index 0000000000000000000000000000000000000000..3f330e444087cced1168954b668cace7ea38884a
--- /dev/null
+++ b/db/post_migrate/20210409185531_remove_members_index_on_user_id.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class RemoveMembersIndexOnUserId < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  INDEX_NAME = 'index_members_on_user_id'
+
+  def up
+    remove_concurrent_index_by_name(:members, INDEX_NAME)
+  end
+
+  def down
+    add_concurrent_index(:members, :user_id, name: INDEX_NAME)
+  end
+end
diff --git a/db/schema_migrations/20210409185501 b/db/schema_migrations/20210409185501
new file mode 100644
index 0000000000000000000000000000000000000000..9aa098eb4958e1206cae2ec573319e8e452a0f3f
--- /dev/null
+++ b/db/schema_migrations/20210409185501
@@ -0,0 +1 @@
+3655b51b9975a73f3b141f53a0e89aba5b90a030abb8f1dfec3d3bcbb08aa1ec
\ No newline at end of file
diff --git a/db/schema_migrations/20210409185531 b/db/schema_migrations/20210409185531
new file mode 100644
index 0000000000000000000000000000000000000000..c399a2e92587ba0667ca5f7ba54e2210599d7c3a
--- /dev/null
+++ b/db/schema_migrations/20210409185531
@@ -0,0 +1 @@
+1ecd19849ca362a360719c46893f793ffc52b08bd85603305e3fd4d43f3b7ef2
\ No newline at end of file
diff --git a/db/structure.sql b/db/structure.sql
index ccb496261d15f0579394ca985069ab2b415159b4..15f14bc5208a2620cfdebd916d6fef8f2beb2545 100644
--- a/db/structure.sql
+++ b/db/structure.sql
@@ -23018,10 +23018,10 @@ CREATE INDEX index_members_on_requested_at ON members USING btree (requested_at)
 
 CREATE INDEX index_members_on_source_id_and_source_type ON members USING btree (source_id, source_type);
 
-CREATE INDEX index_members_on_user_id ON members USING btree (user_id);
-
 CREATE INDEX index_members_on_user_id_created_at ON members USING btree (user_id, created_at) WHERE ((ldap = true) AND ((type)::text = 'GroupMember'::text) AND ((source_type)::text = 'Namespace'::text));
 
+CREATE INDEX index_members_on_user_id_source_id_source_type ON members USING btree (user_id, source_id, source_type);
+
 CREATE INDEX index_merge_request_assignees_on_merge_request_id ON merge_request_assignees USING btree (merge_request_id);
 
 CREATE UNIQUE INDEX index_merge_request_assignees_on_merge_request_id_and_user_id ON merge_request_assignees USING btree (merge_request_id, user_id);