SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a12e343dd55ff2e92a73120dc676c953f98a4f2914172242e72275b2f53fe130' 
  AND token = '9/5Ok5B26qya5qBbW04TzLrknbDKiD5/z6n+PXuQRuw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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