diff --git a/backend/src/db/migrations/20251018061215_sub-org.ts b/backend/src/db/migrations/20251018061215_sub-org.ts
index 6378fa66a..089aeef90 100644
--- a/backend/src/db/migrations/20251018061215_sub-org.ts
+++ b/backend/src/db/migrations/20251018061215_sub-org.ts
@@ -2,7 +2,7 @@ import { Knex } from "knex";
 
 import { dropConstraintIfExists } from "@app/db/migrations/utils/dropConstraintIfExists";
 
-import { AccessScope, TableName } from "../schemas";
+import { TableName } from "../schemas";
 
 export async function up(knex: Knex): Promise<void> {
   const hasParentOrgId = await knex.schema.hasColumn(TableName.Organization, "parentOrgId");
@@ -18,8 +18,6 @@ export async function up(knex: Knex): Promise<void> {
       await dropConstraintIfExists(TableName.Organization, "organizations_slug_unique", knex);
       t.unique(["rootOrgId", "parentOrgId", "slug"]);
     });
-
-    // had to switch to raw for null not distinct
   }
 
   const hasIdentityOrgCol = await knex.schema.hasColumn(TableName.Identity, "orgId");
@@ -28,24 +26,6 @@ export async function up(knex: Knex): Promise<void> {
       t.uuid("orgId");
       t.foreign("orgId").references("id").inTable(TableName.Organization).onDelete("CASCADE");
     });
-
-    await knex.raw(
-      `
-  UPDATE ?? AS identity
-  SET "orgId" = membership."scopeOrgId"
-  FROM ?? AS membership
-  WHERE 
-    membership."actorIdentityId" = identity."id"
-    AND membership."scope" = ?
-`,
-      [TableName.Identity, TableName.Membership, AccessScope.Organization]
-    );
-
-    await knex.raw(`DELETE FROM ?? WHERE "orgId" IS NULL`, [TableName.Identity]);
-
-    await knex.schema.alterTable(TableName.Identity, (t) => {
-      t.uuid("orgId").notNullable().alter();
-    });
   }
 }
 
diff --git a/backend/src/db/migrations/20251019061215_sub-org-identity-backfill.ts b/backend/src/db/migrations/20251019061215_sub-org-identity-backfill.ts
new file mode 100644
index 000000000..9054a03ee
--- /dev/null
+++ b/backend/src/db/migrations/20251019061215_sub-org-identity-backfill.ts
@@ -0,0 +1,48 @@
+import { Knex } from "knex";
+
+import { chunkArray } from "@app/lib/fn";
+
+import { AccessScope, TableName } from "../schemas";
+
+export async function up(knex: Knex): Promise<void> {
+  await knex.transaction(async (tx) => {
+    const hasIdentityOrgCol = await tx.schema.hasColumn(TableName.Identity, "orgId");
+    if (hasIdentityOrgCol) {
+      const identityMemberships = await tx(TableName.Membership)
+        .where({
+          scope: AccessScope.Organization
+        })
+        .whereNotNull("actorIdentityId")
+        .select("actorIdentityId", "scopeOrgId");
+
+      const identityToOrgMapping: Record<string, string> = {};
+      identityMemberships.forEach((el) => {
+        if (el.actorIdentityId) {
+          identityToOrgMapping[el.actorIdentityId] = el.scopeOrgId;
+        }
+      });
+
+      const batchMemberships = chunkArray(identityMemberships, 500);
+      for await (const membership of batchMemberships) {
+        const identityIds = membership.map((el) => el.actorIdentityId).filter(Boolean) as string[];
+        if (identityIds.length) {
+          const identities = await tx(TableName.Identity).whereIn("id", identityIds).select("*");
+          await tx(TableName.Identity)
+            .insert(
+              identities.map((el) => ({
+                ...el,
+                orgId: identityToOrgMapping[el.id]
+              }))
+            )
+            .onConflict("id")
+            .merge();
+        }
+      }
+    }
+  });
+}
+
+export async function down(): Promise<void> {}
+
+const config = { transaction: false };
+export { config };
diff --git a/backend/src/db/migrations/20251028155708_identity-access-token-remove-fk-for-identity-id.ts b/backend/src/db/migrations/20251028155708_identity-access-token-remove-fk-for-identity-id.ts
new file mode 100644
index 000000000..0974f39c2
--- /dev/null
+++ b/backend/src/db/migrations/20251028155708_identity-access-token-remove-fk-for-identity-id.ts
@@ -0,0 +1,22 @@
+import { Knex } from "knex";
+
+import { TableName } from "../schemas";
+
+export async function up(knex: Knex): Promise<void> {
+  await knex.transaction(async (tx) => {
+    await tx.schema.alterTable(TableName.IdentityAccessToken, (table) => {
+      table.dropForeign("identityId");
+    });
+  });
+}
+
+export async function down(knex: Knex): Promise<void> {
+  await knex.transaction(async (tx) => {
+    await tx.schema.alterTable(TableName.IdentityAccessToken, (table) => {
+      table.foreign("identityId").references("id").inTable(TableName.Identity);
+    });
+  });
+}
+
+const config = { transaction: false };
+export { config };
diff --git a/backend/src/db/migrations/20251028160921_delete-no-org-identities.ts b/backend/src/db/migrations/20251028160921_delete-no-org-identities.ts
new file mode 100644
index 000000000..0eb0e7ae0
--- /dev/null
+++ b/backend/src/db/migrations/20251028160921_delete-no-org-identities.ts
@@ -0,0 +1,30 @@
+import { Knex } from "knex";
+
+import { TableName } from "../schemas";
+
+const MIGRATION_TIMEOUT = 30 * 60 * 1000; // 30 minutes
+
+export async function up(knex: Knex): Promise<void> {
+  const result = await knex.raw("SHOW statement_timeout");
+  const originalTimeout = result.rows[0].statement_timeout;
+
+  await knex.transaction(async (tx) => {
+    try {
+      await tx.raw(`SET statement_timeout = ${MIGRATION_TIMEOUT}`);
+      const hasIdentityOrgCol = await tx.schema.hasColumn(TableName.Identity, "orgId");
+      if (hasIdentityOrgCol) {
+        await tx(TableName.Identity).whereNull("orgId").delete();
+        await tx.schema.alterTable(TableName.Identity, (t) => {
+          t.uuid("orgId").notNullable().alter();
+        });
+      }
+    } finally {
+      await tx.raw(`SET statement_timeout = '${originalTimeout}'`);
+    }
+  });
+}
+
+export async function down(): Promise<void> {}
+
+const config = { transaction: false };
+export { config };