SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ed0c78cdef357cdcd51ebfba741e2a314bf569816d388f53813daf078f10091' 
  AND token = 'UQizquEUhD6vk5wCiRVuP5d7UakgWMbQjnF47bqQTow=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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