Jennifer_rivera makes a good point about both factors. Slow systems definitely add to backlogs, but sudden spikes in demand can also crash things. Like when a popular concert sells out, even well-built booking sites have trouble. It's rarely just one or the other.
Totally! See this in public services like the DMV. Backlogs called 'high demand' but really outdated systems. Ticket sites crash, blame traffic not bad servers, a systemic excuse to avoid accountability.