SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '9d5df62a89d6b0e625069727c5c364c9f06d372ae1a5b2b144f9fd92133e9574' 
  AND token = 'YOBJVvQE2fL/+mSwxg0cB0dSvLmqy1p54PrdJOEEcLU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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