SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '851caf9e2ddeb79bb83e8ce639d9e434144bfec974f0698d3042b938cfd1d32e' 
  AND token = 'o6rKTEdA5LrZkTWUuB+RKLrtXfq3A9Ow3D+MpLd5wN8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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