建立「保留」是預訂服務的第一步。合作夥伴後端會確認要求的預約時段是否有效且可供預訂。合作夥伴可於內部針對要求的時段建立暫時性保留，並設為在 lease_expiration_time 後自動到期。後端可修改 lease_expiration_time；舉例來說，要求的保留時間過長時，則可從後端修改。
系統會將已建立的保留傳回用戶端。
// Temporary lease for an inventory slot message Lease { // ID of the lease. Ignored when creating a lease. string lease_id = 1; // ID of the merchant for the slot string merchant_id = 2; // ID of the merchant service string service_id = 3; // Start time of the appointment slot google.protobuf.Timestamp start_time = 4; // Duration of the appointment slot google.protobuf.Duration duration = 5; // Opaque tag that identifies the availability slot and matches the value // provided in the availability feed. string availability_tag = 8; // The set of resources that disambiguates the appointment slot, e.g. by // indicating the staff member and room selected by the user. Resources resources = 9; // Unique identifier for this lease, chosen by the client. Serves as an // idempotency token for [ext.maps.booking.partner.v0.CreateLease] requests. string client_reference = 6; // Expiration time of the lease google.protobuf.Timestamp lease_expiration_time = 7; } // Reference to a [ext.maps.booking.partner.v0.Lease] that has been created via // [ext.maps.booking.partner.v0.CreateLease] message LeaseReference { // Lease ID string lease_id = 1; }