SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3768da46a75596041d3836c7e4fdca8b155083a1d26e6a7ea9c891db56418743' 
  AND token = 'jDVwDBeQowNJfAtZAFXlffd0izC7nQ+hG77YvOpL58s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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