SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c0398f6d6505bdae9e22c1e1d829148ae7e0415c0237aa72494ae0b3aff4fefb' 
  AND token = 'jxVrMbzsHe/ulfmkuKwYC+bC76+OjxxzR6VD6gmLiCA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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