SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a2ed93beedf1f39c878215c138a9fc4ed07077cd03a5fb96316a101e516713c2' 
  AND token = '743qhEKPVT8xWghxlnWAgD5JGRLfJdhyk4q7wQ+92G0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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