SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9a241d6895d66465e4c9ed0b84e836749a3525d88abf69a4e8aa5bf4f5a8704' 
  AND token = '9M8U7epcmVH7RHWnQ5J+YRTpLqWSgGgDQUMvnh+KhQc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00057

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}