SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '98ba820e591257bedc22f6146c1dd03954740103de447a3682125216af8f3cab' 
  AND token = 'Slxn18WUSp27ygNfEYmH3jwHnbgj40JlW7ASJKdyTiU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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