SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '557c717aefeb761730fa098ea7aaf377f8117ec508427333345de55ae7e12c20' 
  AND token = '6/e8AcgEnojNxz/3ZdJ3zgzyxM/KRoHUnvRRJNY1rRs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00064

JSON explain

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