SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4c4310ca8fe64d9df15d3c176255d03cf9503ff641a4c7f4c9c64be892d48108' 
  AND token = 'P9Tz/WNlLZezRQBd9LuFvICnrFLuEhE8lbLgc+Jps/A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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