SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '68291553d13d8c5b62b985f81a9da77b79f1e0decde5e1da4c3ebb0abe7762f7' 
  AND token = 'NG7zPQh3ZKl71Sv0I/+dFYF0Tr0MvjruBwzZiOU0mQo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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