perf: index owner-scoped email timelines

.jules/bolt.md

@@ -54,3 +54,7 @@
 ## 2026-06-18 - Route heavy search reads to read replica
 **Learning:** `backend/api/search.py` needs the primary database session for current provider and tenant configuration, but the heavy email and attachment search query can use the read-only session from `db.session.get_readonly_db`.
 **Action:** Keep provider/config resolution on `Depends(get_db)` and route only the read-only search query through `Depends(get_readonly_db)` so search load moves to replicas without replica-lagging fresh configuration reads.
+
+## 2026-06-19 - Email owner/date lookup index
+**Learning:** Inbox and reply-wait queries commonly scope `email_records` by `user_id` and `organization_id` before ordering or filtering by `date`, so separate single-column indexes still leave the planner with avoidable sort/filter work.
+**Action:** Keep `ix_email_records_owner_date` on `(user_id, organization_id, date)` in both the SQLAlchemy model and bootstrap backfill SQL when optimizing owner-scoped email timelines.

backend/db/models.py

@@ -351,6 +351,12 @@ class Email(Base):
             "message_id",
             name="uq_emails_owner_message_id",
         ),
+        Index(
+            "ix_email_records_owner_date",
+            "user_id",
+            "organization_id",
+            "date",
+        ),
     )
 
     id: Mapped[int] = mapped_column(primary_key=True)

backend/scripts/bootstrap_db.py

@@ -145,6 +145,10 @@ def _get_create_indexes_statements() -> list[Executable]:
             "CREATE INDEX IF NOT EXISTS ix_email_records_organization_id "
             "ON email_records (organization_id)"
         ),
+        text(
+            "CREATE INDEX IF NOT EXISTS ix_email_records_owner_date "
+            "ON email_records (user_id, organization_id, date)"
+        ),
         text(
             "CREATE INDEX IF NOT EXISTS ix_sender_relationships_owner_source "
             "ON sender_relationships "

backend/tests/test_bootstrap_db.py

@@ -10,6 +10,7 @@
 from db.models import (
     CalendarWritebackSource,
     ConnectorSignalEvent,
+    Email,
     ProjectFolder,
     SecurityAuditEvent,
     SenderRelationship,
@@ -103,6 +104,11 @@ def test_schema_backfill_adds_email_indexes(monkeypatch):
         "create index if not exists ix_email_records_organization_id" in statement
         for statement in statements
     )
+    assert any(
+        "create index if not exists ix_email_records_owner_date" in statement
+        and "user_id, organization_id, date" in statement
+        for statement in statements
+    )
     assert any(
         "drop index if exists ix_email_records_message_id" in statement
         for statement in statements
@@ -414,6 +420,19 @@ def test_sender_relationship_model_declares_source_unique_index():
     assert "source_thread_id" in expression_text
 
 
+def test_email_model_declares_owner_date_index():
+    indexes = {index.name: index for index in Email.__table__.indexes}
+
+    owner_date_index = indexes["ix_email_records_owner_date"]
+
+    assert owner_date_index.unique is False
+    assert [column.name for column in owner_date_index.columns] == [
+        "user_id",
+        "organization_id",
+        "date",
+    ]
+
+
 def test_tenant_config_model_declares_owner_scope_unique_index():
     indexes = {index.name: index for index in TenantConfig.__table__.indexes}