SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '790beb71baea7a595403fc752148426c298b5bf0118c75c1adaf3435137a7ea7' 
  AND token = 'W6JmRA2VQJsIS6kW/b92KtzkXroy2sza2jGOZXIRcJw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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