SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e510ca7c98798439f033942fcb78b3867f3c79d2aea430e79e07a789a346fb07' 
  AND token = 'pQRqYjCQripBb1vq9orj3qa9CwAcMTKoJePdZuTgPvs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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