SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '756c744b8c32e80d877fa5dd00b1584d578840365c4fbc29907c45f2f2123709' 
  AND token = 'A256j6Ioko/qiWY32LxBCDB7joGgZoySUvyz/vfBbjg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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