SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a27513bbfc7fae61557060bea8b9b537b31d60f016a5dc1e688592499bc34c00' 
  AND token = 'onBIBBh1t/ZBOuZ5CvUGdzLNV7GdXY5CWvnJNbQQXh8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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