The old software* has been around since the early 2000s, and is a Windows application written in c++. The newer one has a C++/Linux backend, but the UI is basde on Javascript/HTML5/Chromium.
Having tried the new software, the UI performance is appalling - it feels slugggish, much like playing a video game on an underpowered PC, so seeing a generally too low framerate, which at key points drops even lower. Is this likely to be due the technologies used? I don't know much about UI coding, but would've assumed that a C++ application would perform better than one based on Javascript and Chromium.
* https://www.tradingtechnologies.com/trading/xtrader-platform/
** https://www.tradingtechnologies.com/trading/tt-platform/