TORONTO — Like a classroom full of overachieving students, cities around the world are racing to declare themselves “smart” — using sensors, data and ubiquitous cameras to make themselves more efficient, safe and sustainable. Perhaps the most famous initiative is here in Toronto, where Sidewalk Labs, a sibling company to Google, recently released a 1,500-page master plan to remake two neighborhoods with things like snow-melting roads and an underground pneumatic-tube network.

Smart cities make two fundamental promises: lots of data, and automated decision making based on that data. The ultimate smart city will require a raft of existing and to-be-invented technologies, from sensors to robots to artificial intelligence. For many this promises a more efficient, equitable city; for others, it raises questions about privacy and algorithmic bias.

But there is a more basic concern when it comes to smart cities: They will be exceedingly complex to manage, with all sorts of unpredictable vulnerabilities. There will always be a place for new technology in our urban infrastructure, but we may find that often, “dumb” cities will do better than smart ones.

As we know all too well from our personal lives, tech products have a short reliable life span. We accept regular disruptions in internet and cellphone function as a fact of life. Technology ages rapidly, with glitches increasing common only a couple of years into its life.