diff --git a/backend/app/models.py b/backend/app/models.py
index be047e8..29d7b5a 100644
--- a/backend/app/models.py
+++ b/backend/app/models.py
@@ -4,7 +4,7 @@
 """
 from __future__ import annotations
 
-from datetime import date, datetime, timezone
+from datetime import date, datetime
 
 from sqlalchemy import (
     JSON,
@@ -23,9 +23,9 @@ from sqlalchemy import (
 )
 from sqlmodel import Field, SQLModel
 
+from app.core.timeutil import utcnow
+
 
-def _utcnow() -> datetime:
-    return datetime.now(timezone.utc)
 
 
 # ─── Справочники: дополнения и фракции ───────────────────────────────────────
@@ -38,7 +38,7 @@ class Expansion(SQLModel, table=True):
     name_ru: str = Field(sa_column=Column(String(64), nullable=False))
     is_base: bool = Field(sa_column=Column(Boolean, nullable=False, server_default="0"))
     sort_order: int = Field(default=0, nullable=False)
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 class Faction(SQLModel, table=True):
@@ -56,7 +56,7 @@ class Faction(SQLModel, table=True):
         )
     )
     sort_order: int = Field(default=0, nullable=False)
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 # ─── Пользователи и идентичности ─────────────────────────────────────────────
@@ -125,10 +125,10 @@ class User(SQLModel, table=True):
     # Выбранный титул (slug ачивки), отображаемый под ником. Задел: пока всегда NULL
     # (выдача ачивок игрокам — следующий этап).
     title_achievement_slug: str | None = Field(sa_column=Column(String(64), nullable=True))
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
     updated_at: datetime = Field(
-        default_factory=_utcnow,
-        sa_column_kwargs={"onupdate": _utcnow},
+        default_factory=utcnow,
+        sa_column_kwargs={"onupdate": utcnow},
         nullable=False,
     )
 
@@ -150,7 +150,7 @@ class UserAchievement(SQLModel, table=True):
         )
     )
     achievement_slug: str = Field(sa_column=Column(String(64), nullable=False))
-    earned_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    earned_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 class AuthIdentity(SQLModel, table=True):
@@ -167,7 +167,7 @@ class AuthIdentity(SQLModel, table=True):
     )
     provider: str = Field(sa_column=Column(String(16), nullable=False))
     external_id: str = Field(sa_column=Column(String(64), nullable=False))
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 # ─── Группы и членство ───────────────────────────────────────────────────────
@@ -182,10 +182,10 @@ class Group(SQLModel, table=True):
             Integer, ForeignKey("users.id", ondelete="RESTRICT"), nullable=False, index=True
         )
     )
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
     updated_at: datetime = Field(
-        default_factory=_utcnow,
-        sa_column_kwargs={"onupdate": _utcnow},
+        default_factory=utcnow,
+        sa_column_kwargs={"onupdate": utcnow},
         nullable=False,
     )
 
@@ -209,7 +209,7 @@ class GroupMember(SQLModel, table=True):
         )
     )
     role: str = Field(default="member", sa_column=Column(String(16), nullable=False, server_default="member"))
-    joined_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    joined_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 class GroupInvitation(SQLModel, table=True):
@@ -237,7 +237,7 @@ class GroupInvitation(SQLModel, table=True):
             Integer, ForeignKey("users.id", ondelete="SET NULL"), nullable=True
         )
     )
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 class GroupExpansion(SQLModel, table=True):
@@ -257,7 +257,7 @@ class GroupExpansion(SQLModel, table=True):
             Integer, ForeignKey("expansions.id", ondelete="RESTRICT"), nullable=False
         )
     )
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 # ─── Партии и участники ──────────────────────────────────────────────────────
@@ -295,10 +295,10 @@ class Match(SQLModel, table=True):
             Integer, ForeignKey("users.id", ondelete="RESTRICT"), nullable=False, index=True
         )
     )
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
     updated_at: datetime = Field(
-        default_factory=_utcnow,
-        sa_column_kwargs={"onupdate": _utcnow},
+        default_factory=utcnow,
+        sa_column_kwargs={"onupdate": utcnow},
         nullable=False,
     )
 
@@ -333,7 +333,7 @@ class MatchParticipant(SQLModel, table=True):
     eliminated: bool = Field(sa_column=Column(Boolean, nullable=False, server_default="0"))
     was_random: bool = Field(sa_column=Column(Boolean, nullable=False, server_default="0"))
     comment: str | None = Field(sa_column=Column(Text, nullable=True))
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 class MatchAttachment(SQLModel, table=True):
@@ -359,7 +359,7 @@ class MatchAttachment(SQLModel, table=True):
     storage_path: str = Field(sa_column=Column(String(255), nullable=False))
     mime_type: str = Field(sa_column=Column(String(64), nullable=False))
     size_bytes: int = Field(sa_column=Column(Integer, nullable=False))
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 # ─── Уведомления ─────────────────────────────────────────────────────────────
@@ -387,7 +387,7 @@ class Notification(SQLModel, table=True):
     body: str | None = Field(default=None, sa_column=Column(Text, nullable=True))
     link: str | None = Field(default=None, sa_column=Column(String(255), nullable=True))
     read_at: datetime | None = Field(default=None, sa_column=Column(DateTime, nullable=True))
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False, index=True)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False, index=True)
 
 
 # ─── Журнал аудита ───────────────────────────────────────────────────────────
@@ -411,7 +411,7 @@ class AuditLog(SQLModel, table=True):
     payload: dict | None = Field(default=None, sa_column=Column(JSON, nullable=True))
     ip: str | None = Field(sa_column=Column(String(45), nullable=True))
     user_agent: str | None = Field(sa_column=Column(String(256), nullable=True))
-    created_at: datetime = Field(default_factory=_utcnow, nullable=False)
+    created_at: datetime = Field(default_factory=utcnow, nullable=False)
 
 
 # Заготовка под будущие вложения (НЕ в v1-миграции, добавится отдельно):
diff --git a/backend/app/services/attachment_service.py b/backend/app/services/attachment_service.py
index eabfe2e..3847779 100644
--- a/backend/app/services/attachment_service.py
+++ b/backend/app/services/attachment_service.py
@@ -11,7 +11,6 @@ from sqlmodel import Session, select
 
 from app.core.config import settings
 from app.core.errors import ConflictError, NotFoundError
-from app.core.timeutil import utcnow
 from app.models import Match, MatchAttachment, User
 
 MAX_ATTACHMENTS = 10
@@ -40,17 +39,11 @@ def file_path(att: MatchAttachment) -> Path:
     return Path(settings.upload_dir) / att.storage_path
 
 
-def _touch(session: Session, match: Match) -> None:
-    """Двинуть версию партии: набор вложений виден в MatchRead, а сама строка matches
-    при работе с ними не меняется — без этого оптимистичная блокировка проспала бы
-    конкурентную правку."""
-    match.updated_at = utcnow()
-    session.add(match)
-
-
 def add_photo(
     session: Session, match: Match, user: User, content: bytes, ext: str, mime: str
 ) -> MatchAttachment:
+    from app.services import match_service  # избегаем цикла импорта
+
     if count(session, match.id) >= MAX_ATTACHMENTS:  # type: ignore[arg-type]
         raise ConflictError(f"Можно прикрепить не более {MAX_ATTACHMENTS} файлов.")
     att = MatchAttachment(
@@ -69,7 +62,7 @@ def add_photo(
     abs_path.write_bytes(content)
     att.storage_path = rel
     session.add(att)
-    _touch(session, match)
+    match_service.touch(session, match)
     session.commit()
     session.refresh(att)
     return att
@@ -83,6 +76,8 @@ def get_for_match(session: Session, match_id: int, att_id: int) -> MatchAttachme
 
 
 def delete(session: Session, match: Match, att_id: int) -> None:
+    from app.services import match_service  # избегаем цикла импорта
+
     att = get_for_match(session, match.id, att_id)  # type: ignore[arg-type]
     path = file_path(att)
     if path.exists():
@@ -91,7 +86,7 @@ def delete(session: Session, match: Match, att_id: int) -> None:
         except OSError:
             pass
     session.delete(att)
-    _touch(session, match)
+    match_service.touch(session, match)
     session.commit()
 
 
diff --git a/backend/app/services/invitation_service.py b/backend/app/services/invitation_service.py
index 5796e97..3b77c86 100644
--- a/backend/app/services/invitation_service.py
+++ b/backend/app/services/invitation_service.py
@@ -5,6 +5,7 @@ GroupMember). Лимит участников — общий с membership_servi
 """
 from __future__ import annotations
 
+from sqlalchemy.orm import aliased
 from sqlmodel import Session, select
 
 from app.core.errors import ConflictError, NotFoundError, ValidationError
@@ -70,17 +71,17 @@ def create_invitation(
 
 
 def list_for_user(session: Session, user_id: int) -> list[dict]:
+    inviter = aliased(User)
     rows = session.exec(
-        select(GroupInvitation, Group.name).join(Group, Group.id == GroupInvitation.group_id)
+        select(GroupInvitation, Group.name, inviter.nickname)
+        .join(Group, Group.id == GroupInvitation.group_id)
+        # LEFT JOIN: пригласивший мог быть удалён (invited_by_id → SET NULL).
+        .join(inviter, inviter.id == GroupInvitation.invited_by_id, isouter=True)
         .where(GroupInvitation.user_id == user_id)
         .order_by(GroupInvitation.created_at.desc())
     ).all()
     out = []
-    for inv, gname in rows:
-        inviter_nick = None
-        if inv.invited_by_id is not None:
-            inviter = session.get(User, inv.invited_by_id)
-            inviter_nick = inviter.nickname if inviter else None
+    for inv, gname, inviter_nick in rows:
         out.append(
             {
                 "id": inv.id,
diff --git a/backend/app/services/match_service.py b/backend/app/services/match_service.py
index e3d7ecb..6639686 100644
--- a/backend/app/services/match_service.py
+++ b/backend/app/services/match_service.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 
 import random
 from dataclasses import dataclass
-from datetime import date, datetime, timezone
+from datetime import date
 
 from sqlmodel import Session, select
 
@@ -16,7 +16,7 @@ from app.core.errors import (
     NotFoundError,
     ValidationError,
 )
-from app.core.timeutil import app_today, iso_utc
+from app.core.timeutil import app_today, iso_utc, utcnow
 from app.models import Faction, GroupMember, Match, MatchParticipant, User
 from app.services import group_service
 
@@ -56,10 +56,6 @@ class ParticipantInput:
     comment: str | None = None
 
 
-def _utcnow() -> datetime:
-    return datetime.now(timezone.utc)
-
-
 def round_to_30(minutes: float) -> int:
     """Округление длительности до получаса, минимум 30 минут."""
     return max(30, int(round(minutes / 30.0)) * 30)
@@ -77,6 +73,17 @@ def match_version(match: Match) -> str:
     return iso_utc(match.updated_at)
 
 
+def touch(session: Session, match: Match) -> None:
+    """Пометить партию изменённой (без commit).
+
+    Версия для оптимистичной блокировки — это updated_at, а onupdate у SQLAlchemy
+    срабатывает только при реальном UPDATE строки matches. Правки, меняющие лишь
+    связанные сущности (участники, вложения), строку не трогают, поэтому каждая
+    такая точка обязана позвать touch — иначе конкурентная запись пройдёт молча."""
+    match.updated_at = utcnow()
+    session.add(match)
+
+
 def assert_version(match: Match, expected: str | None) -> None:
     """Если клиент прислал версию и она устарела — отказываем (кто-то изменил партию)."""
     if expected is not None and expected != match_version(match):
@@ -188,7 +195,7 @@ def create_match(
         session, group_id, [r.user_id for r in roster], [r.faction_id for r in roster]
     )
 
-    now = _utcnow()
+    now = utcnow()
     match = Match(
         group_id=group_id,
         status="in_progress",
@@ -264,7 +271,7 @@ def finish_match(
             p.faction_id = f.faction_id
         session.add(p)
 
-    now = _utcnow()
+    now = utcnow()
     match.finished_at = now
     started = match.started_at
     if started is not None:
@@ -351,11 +358,7 @@ def update_match(
             )
         match.player_count = len(participants)
 
-    # Версия партии = updated_at, а onupdate срабатывает только при реальном UPDATE
-    # строки matches. Правка одних участников его не вызывает, и тогда оптимистичная
-    # блокировка молча пропускала бы конкурентную запись — поэтому бампаем явно.
-    match.updated_at = _utcnow()
-    session.add(match)
+    touch(session, match)
     session.commit()
     session.refresh(match)
     return match
diff --git a/backend/app/services/membership_service.py b/backend/app/services/membership_service.py
index 12b4dd4..18b8fba 100644
--- a/backend/app/services/membership_service.py
+++ b/backend/app/services/membership_service.py
@@ -5,6 +5,7 @@ from sqlmodel import Session, select
 
 from app.core.errors import ConflictError, ForbiddenError, NotFoundError, ValidationError
 from app.models import Group, GroupMember, User
+from app.services import group_service
 
 MAX_GROUP_SIZE = 10
 
@@ -33,11 +34,7 @@ def add_member_by_nickname(session: Session, group: Group, nickname: str) -> tup
     if member_count >= MAX_GROUP_SIZE:
         raise ConflictError(f"В группе уже максимум участников ({MAX_GROUP_SIZE}).")
 
-    existing = session.exec(
-        select(GroupMember).where(
-            GroupMember.group_id == group.id, GroupMember.user_id == user.id
-        )
-    ).first()
+    existing = group_service.get_membership(session, group.id, user.id)
     if existing is not None:
         raise ConflictError("Игрок уже в группе.")
 
@@ -48,22 +45,26 @@ def add_member_by_nickname(session: Session, group: Group, nickname: str) -> tup
     return member, user
 
 
-def remove_member(session: Session, group: Group, user_id: int) -> None:
-    member = session.exec(
-        select(GroupMember).where(
-            GroupMember.group_id == group.id, GroupMember.user_id == user_id
+def _assert_not_last_owner(session: Session, group: Group, member: GroupMember, message: str) -> None:
+    """Группа без владельца неисправима: назначить нового становится некому."""
+    if member.role != "owner":
+        return
+    owners = session.exec(
+        select(GroupMember.id).where(
+            GroupMember.group_id == group.id, GroupMember.role == "owner"
         )
-    ).first()
+    ).all()
+    if len(owners) <= 1:
+        raise ForbiddenError(message)
+
+
+def remove_member(session: Session, group: Group, user_id: int) -> None:
+    member = group_service.get_membership(session, group.id, user_id)
     if member is None:
         raise NotFoundError("Игрок не состоит в группе.")
-    if member.role == "owner":
-        owners = session.exec(
-            select(GroupMember).where(
-                GroupMember.group_id == group.id, GroupMember.role == "owner"
-            )
-        ).all()
-        if len(owners) <= 1:
-            raise ForbiddenError("Нельзя удалить последнего владельца группы.")
+    _assert_not_last_owner(
+        session, group, member, "Нельзя удалить последнего владельца группы."
+    )
 
     # Сбросить активную группу у тех, для кого она была активной.
     user = session.get(User, user_id)
@@ -78,23 +79,13 @@ def remove_member(session: Session, group: Group, user_id: int) -> None:
 def change_role(session: Session, group: Group, user_id: int, role: str) -> GroupMember:
     if role not in ("owner", "member"):
         raise ValidationError("Недопустимая роль.")
-    member = session.exec(
-        select(GroupMember).where(
-            GroupMember.group_id == group.id, GroupMember.user_id == user_id
-        )
-    ).first()
+    member = group_service.get_membership(session, group.id, user_id)
     if member is None:
         raise NotFoundError("Игрок не состоит в группе.")
-    if member.role == "owner" and role != "owner":
-        # Без этого единственный владелец мог разжаловать сам себя, и группа
-        # оставалась без владельца навсегда: назначить нового уже некому.
-        owners = session.exec(
-            select(GroupMember).where(
-                GroupMember.group_id == group.id, GroupMember.role == "owner"
-            )
-        ).all()
-        if len(owners) <= 1:
-            raise ForbiddenError("Нельзя снять роль с последнего владельца группы.")
+    if role != "owner":
+        _assert_not_last_owner(
+            session, group, member, "Нельзя снять роль с последнего владельца группы."
+        )
     member.role = role
     session.add(member)
     session.commit()
diff --git a/backend/app/services/stats_service.py b/backend/app/services/stats_service.py
index 690f537..d90575b 100644
--- a/backend/app/services/stats_service.py
+++ b/backend/app/services/stats_service.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 
 from typing import Any
 
-from sqlalchemy import text
+from sqlalchemy import func, text
 from sqlmodel import Session, select
 
 from app.core.timeutil import iso_utc
@@ -235,12 +235,13 @@ def profile_stats(session: Session, user_id: int, group_id: int | None = None) -
 
 def group_stats(session: Session, group_id: int) -> dict:
     board = leaderboard(session, group_id=group_id)
-    total_matches = session.exec(
-        select(Match).where(Match.group_id == group_id, Match.status == "finished")
-    ).all()
-    last_at = None
-    if total_matches:
-        last_at = str(max(m.played_at for m in total_matches))
+    # Нужны только счётчик и дата последней партии — тянуть строки целиком незачем.
+    games_count, last_played = session.exec(
+        select(func.count(), func.max(Match.played_at)).where(
+            Match.group_id == group_id, Match.status == "finished"
+        )
+    ).one()
+    last_at = str(last_played) if last_played else None
 
     available_ids = group_service.available_faction_ids(session, group_id)
     faction_meta = []
@@ -290,7 +291,7 @@ def group_stats(session: Session, group_id: int) -> dict:
 
     return {
         "group_id": group_id,
-        "total_matches": len(total_matches),
+        "total_matches": games_count,
         "last_match_at": last_at,
         "leaderboard": board["entries"],
         "provisional": board["provisional"],
@@ -300,26 +301,44 @@ def group_stats(session: Session, group_id: int) -> dict:
     }
 
 
+def _participant_row(p: MatchParticipant, u: User, f: Faction) -> dict:
+    return {
+        "user_id": u.id,
+        "nickname": u.nickname,
+        "faction_id": f.id,
+        "faction_name": f.name_ru,
+        "place": p.place,
+        "eliminated": p.eliminated,
+        "was_random": p.was_random,
+        "comment": p.comment,
+    }
+
+
+def _participants_by_match(session: Session, match_ids: list[int]) -> dict[int, list[dict]]:
+    """Участники сразу всей страницы партий: иначе запрос на каждую партию (N+1)."""
+    if not match_ids:
+        return {}
+    rows = session.exec(
+        select(MatchParticipant, User, Faction)
+        .join(User, User.id == MatchParticipant.user_id)
+        .join(Faction, Faction.id == MatchParticipant.faction_id)
+        .where(MatchParticipant.match_id.in_(match_ids))
+        # place может быть NULL (партия идёт) — NULL уходит в конец сортировки.
+        .order_by(MatchParticipant.place.is_(None), MatchParticipant.place, User.nickname)
+    ).all()
+    out: dict[int, list[dict]] = {}
+    for p, u, f in rows:
+        out.setdefault(p.match_id, []).append(_participant_row(p, u, f))
+    return out
+
+
 def _match_items(session: Session, matches) -> list[dict]:
     """Элементы списка партий (общее для списка группы и истории игрока)."""
-    from app.services.match_service import participants_detail  # избегаем цикла импорта
+    by_match = _participants_by_match(session, [m.id for m in matches])
 
     items = []
     for m in matches:
-        parts = []
-        for p, u, f in participants_detail(session, m.id):  # type: ignore[arg-type]
-            parts.append(
-                {
-                    "user_id": u.id,
-                    "nickname": u.nickname,
-                    "faction_id": f.id,
-                    "faction_name": f.name_ru,
-                    "place": p.place,
-                    "eliminated": p.eliminated,
-                    "was_random": p.was_random,
-                    "comment": p.comment,
-                }
-            )
+        parts = by_match.get(m.id, [])
         items.append(
             {
                 "id": m.id,
@@ -339,7 +358,9 @@ def _match_items(session: Session, matches) -> list[dict]:
 
 
 def group_match_list(session: Session, group_id: int, limit: int = 20, offset: int = 0) -> dict:
-    total = len(session.exec(select(Match.id).where(Match.group_id == group_id)).all())
+    total = session.exec(
+        select(func.count()).select_from(Match).where(Match.group_id == group_id)
+    ).one()
     matches = session.exec(
         select(Match)
         .where(Match.group_id == group_id)
@@ -385,13 +406,12 @@ def user_match_list(
         }
 
     where = (MatchParticipant.user_id == user_id, Match.status == "finished")
-    total = len(
-        session.exec(
-            select(Match.id)
-            .join(MatchParticipant, MatchParticipant.match_id == Match.id)
-            .where(*where)
-        ).all()
-    )
+    total = session.exec(
+        select(func.count())
+        .select_from(Match)
+        .join(MatchParticipant, MatchParticipant.match_id == Match.id)
+        .where(*where)
+    ).one()
     matches = session.exec(
         select(Match)
         .join(MatchParticipant, MatchParticipant.match_id == Match.id)
@@ -410,8 +430,6 @@ def user_match_list(
 
 def user_in_progress_matches(session: Session, user_id: int) -> list[dict]:
     """Незавершённые партии во всех группах, где состоит пользователь (новые сверху)."""
-    from app.services.match_service import participants_detail  # избегаем цикла импорта
-
     group_ids = list(
         session.exec(select(GroupMember.group_id).where(GroupMember.user_id == user_id)).all()
     )
@@ -423,21 +441,10 @@ def user_in_progress_matches(session: Session, user_id: int) -> list[dict]:
         .where(Match.status == "in_progress", Match.group_id.in_(group_ids))
         .order_by(Match.started_at.desc(), Match.id.desc())
     ).all()
+    by_match = _participants_by_match(session, [m.id for m, _ in rows])
     out = []
     for m, gname in rows:
-        parts = [
-            {
-                "user_id": u.id,
-                "nickname": u.nickname,
-                "faction_id": f.id,
-                "faction_name": f.name_ru,
-                "place": p.place,
-                "eliminated": p.eliminated,
-                "was_random": p.was_random,
-                "comment": p.comment,
-            }
-            for p, u, f in participants_detail(session, m.id)  # type: ignore[arg-type]
-        ]
+        parts = by_match.get(m.id, [])
         out.append(
             {
                 "id": m.id,