SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '104f328efe446576d7f3e41500918f2ee53adb110fa04962ae6b93365fd48d55' 
  AND token = 'nY5sSfQq/+ySA76iQVDvRn4EFIqARZcESm1vaxNwGs4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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