The recent Invision update was just bug fixes and removal of some deprecated admin features.
We have to update other software too, not just Invision. This includes things like web server software, database software, anti virus software, mail server software. - Plus the operating system itself (Ubuntu) The list goes on... Over time, they consume more resources which is unfortunately the nature of software development but luckily hardware technology advances too. - though at a cost. Ultimately there becomes a point where we have to upgrade. Our current web server has lasted us over 3 years which seems reasonable. If we don't keep on top of this the site will be become slow, unreliable, glitchy and potentially insecure. We follow best practices to avoid this.
Also, site activity has increased in recent months, particularly the number of concurrent online users during peak times. I haven't drilled deep into the stats, but definitely an observation - this too will result in higher memory utilisation.
This is at an increased cost to Canal World which as you know is funded entirely from member donations. All donations appreciated. 🙂