SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ef64f2608f6a0a59bd5990b4ab637b3a1e49d0bee1776bf07743ac985643cea5' 
  AND token = '+B8MR9BkIjVdUz2mLGziM1IEEUwe/+V3h4PnO3/Cank=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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