SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a0df4821bc21006e438f639afeb98980c946f37c62297951993026eccc6ceec' 
  AND token = 'FhMIQmu1RdVDvaZ2dp73QRsGjInxmiUTDd2wWlHTceo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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