SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd73ace5158da95411bbb81001a9af0a0d8eab160761ead6270b388c832a8ee6f' 
  AND token = 'TloMv+xTwmL662fQ8takWmGGZOy+qrLKtlsEdGTmQDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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