SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8b251462372def17d470e0fcc709aaa67ad51a32be39bec9fffd24b49e454f3' 
  AND token = 'NMc42CcOEwJUu27mlb50tO8hZkaMIoE23QPWXbsFGz0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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