SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '73d9839518ec46494679c5bb2012ad942ba03560979985fd2cad5469538809ab' 
  AND token = 'txiAwFCellohAJs0dSlTsQ/FFjZ/l3wMqya3zbjbEsE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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