SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '28b7dccf9bbfaa8a88b41141ea0e774e185adb09983b44f9248881430e9042a4' 
  AND token = 'uRFIo0oFvqnMnHFy96ys3Leokvn5DWcKZpriHUtgGaY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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