diff --git a/backend/libraries/group_chat_core/src/members.rs b/backend/libraries/group_chat_core/src/members.rs
index 351071edac..f381f70d87 100644
--- a/backend/libraries/group_chat_core/src/members.rs
+++ b/backend/libraries/group_chat_core/src/members.rs
@@ -652,26 +652,57 @@ pub struct ChangeRoleSuccess {
     pub prev_role: GroupRoleInternal,
 }
 
-#[derive(Clone)]
+#[derive(Serialize, Deserialize, Clone)]
 pub struct GroupMemberInternal {
+    #[serde(rename = "u")]
     user_id: UserId,
+    #[serde(rename = "d")]
     date_added: TimestampMillis,
+    #[serde(rename = "r", default, skip_serializing_if = "is_default")]
     role: Timestamped<GroupRoleInternal>,
+    #[serde(
+        rename = "n",
+        default = "default_notifications_muted",
+        skip_serializing_if = "is_default_notifications_muted"
+    )]
     notifications_muted: Timestamped<bool>,
+    #[serde(rename = "m", default, skip_serializing_if = "Mentions::is_empty")]
     pub mentions: Mentions,
+    #[serde(rename = "tf", default, skip_serializing_if = "TimestampedSet::is_empty")]
     pub followed_threads: TimestampedSet<MessageIndex>,
+    #[serde(rename = "tu", default, skip_serializing_if = "TimestampedSet::is_empty")]
     pub unfollowed_threads: TimestampedSet<MessageIndex>,
+    #[serde(rename = "p", default, skip_serializing_if = "BTreeSet::is_empty")]
     proposal_votes: BTreeSet<(TimestampMillis, MessageIndex)>,
+    #[serde(rename = "pr", default, skip_serializing_if = "is_default")]
     latest_proposal_vote_removed: TimestampMillis,
+    #[serde(rename = "s", default, skip_serializing_if = "is_default")]
     suspended: Timestamped<bool>,
+    #[serde(rename = "ra", default, skip_serializing_if = "is_default")]
     pub rules_accepted: Option<Timestamped<Version>>,
+    #[serde(rename = "ut", default, skip_serializing_if = "is_default")]
     user_type: UserType,
+    #[serde(rename = "me", default, skip_serializing_if = "is_default")]
     min_visible_event_index: EventIndex,
+    #[serde(rename = "mm", default, skip_serializing_if = "is_default")]
     min_visible_message_index: MessageIndex,
+    #[serde(rename = "la", default, skip_serializing_if = "is_default")]
     lapsed: Timestamped<bool>,
 }
 
 impl GroupMemberInternal {
+    pub fn set_default_timestamps(&mut self) {
+        if self.role.timestamp <= self.date_added {
+            self.role.timestamp = 0;
+        }
+        if self.notifications_muted.timestamp <= self.date_added {
+            self.notifications_muted.timestamp = 0;
+        }
+        if self.lapsed.timestamp <= self.date_added {
+            self.lapsed.timestamp = 0;
+        }
+    }
+
     pub fn user_id(&self) -> UserId {
         self.user_id
     }
@@ -913,18 +944,6 @@ impl GroupMemberStableStorage {
             lapsed: self.lapsed,
         }
     }
-
-    pub fn set_default_timestamps(&mut self) {
-        if self.role.timestamp <= self.date_added {
-            self.role.timestamp = 0;
-        }
-        if self.notifications_muted.timestamp <= self.date_added {
-            self.notifications_muted.timestamp = 0;
-        }
-        if self.lapsed.timestamp <= self.date_added {
-            self.lapsed.timestamp = 0;
-        }
-    }
 }
 
 impl From<GroupMemberInternal> for GroupMemberStableStorage {
diff --git a/backend/libraries/group_chat_core/src/members_map.rs b/backend/libraries/group_chat_core/src/members_map.rs
index d320253a8c..ee425476a5 100644
--- a/backend/libraries/group_chat_core/src/members_map.rs
+++ b/backend/libraries/group_chat_core/src/members_map.rs
@@ -1,4 +1,4 @@
-use crate::{GroupMemberInternal, GroupMemberStableStorage};
+use crate::GroupMemberInternal;
 use serde::de::{SeqAccess, Visitor};
 use serde::ser::SerializeSeq;
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
@@ -16,38 +16,38 @@ pub trait MembersMap {
 }
 
 pub struct HeapMembersMap {
-    map: BTreeMap<UserId, GroupMemberStableStorage>,
+    map: BTreeMap<UserId, GroupMemberInternal>,
 }
 
 impl HeapMembersMap {
     pub fn new(member: GroupMemberInternal) -> Self {
         HeapMembersMap {
-            map: [(member.user_id(), member.into())].into_iter().collect(),
+            map: [(member.user_id(), member)].into_iter().collect(),
         }
     }
 
     // TODO Remove after next upgrade
-    pub fn values_mut(&mut self) -> impl Iterator<Item = &mut GroupMemberStableStorage> + '_ {
+    pub fn values_mut(&mut self) -> impl Iterator<Item = &mut GroupMemberInternal> + '_ {
         self.map.values_mut()
     }
 }
 
 impl MembersMap for HeapMembersMap {
     fn get(&self, user_id: &UserId) -> Option<GroupMemberInternal> {
-        self.map.get(user_id).cloned().map(|g| g.hydrate(*user_id))
+        self.map.get(user_id).cloned()
     }
 
     fn insert(&mut self, member: GroupMemberInternal) {
-        self.map.insert(member.user_id(), member.into());
+        self.map.insert(member.user_id(), member);
     }
 
     fn remove(&mut self, user_id: &UserId) -> Option<GroupMemberInternal> {
-        self.map.remove(user_id).map(|g| g.hydrate(*user_id))
+        self.map.remove(user_id)
     }
 
     #[cfg(test)]
     fn all_members(&self) -> Vec<GroupMemberInternal> {
-        self.map.iter().map(|(k, v)| v.clone().hydrate(*k)).collect()
+        self.map.values().cloned().collect()
     }
 }
 
@@ -57,12 +57,8 @@ impl Serialize for HeapMembersMap {
         S: Serializer,
     {
         let mut seq = serializer.serialize_seq(Some(self.map.len()))?;
-        for (user_id, member) in self.map.iter() {
-            let value = GroupMembersMapEntry {
-                user_id: *user_id,
-                details: member.clone(),
-            };
-            seq.serialize_element(&value)?;
+        for member in self.map.values() {
+            seq.serialize_element(member)?;
         }
         seq.end()
     }
@@ -91,17 +87,9 @@ impl<'de> Visitor<'de> for GroupMembersMapVisitor {
         A: SeqAccess<'de>,
     {
         let mut map = BTreeMap::new();
-        while let Some(next) = seq.next_element::<GroupMembersMapEntry>()? {
-            map.insert(next.user_id, next.details);
+        while let Some(next) = seq.next_element::<GroupMemberInternal>()? {
+            map.insert(next.user_id(), next);
         }
         Ok(HeapMembersMap { map })
     }
 }
-
-#[derive(Serialize, Deserialize)]
-struct GroupMembersMapEntry {
-    #[serde(rename = "u")]
-    user_id: UserId,
-    #[serde(flatten)]
-    details: GroupMemberStableStorage,
-}