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Comment by polished85 | Hacker News Reader

I initially thought part of the appeal was offloading the workload to the front end, where your processing power scales infinitely with each user's device. Maybe the benefit turned out to be negligible, I'm not really sure. Can server costs be reduced by offloading the work to the front end?

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They absolutely can, if your workload is ideal for this situation, but unfortunately, the most "expensive" (in terms of time, money, computing power, you name it) part of giving a user information is typically the filtering and collation of that information from a much larger pool of information — almost always a pool of information that is far too big and too private to just send to the client to sort through locally.

Even in the most simple scenarios, you quickly find your limits. If you get data back, but it's paginated (and it almost always has to be, for basic reliability reasons as much as anything else), you can't be guaranteed to have the complete set of data in a given circumstance, so you can't perform operations like filtering, pivoting, or sorting that data locally. You have to ask the server to do this for you and wait for the response, just like we've had to in the past.

Dynamic loading of content is a feature of SPAs, but it's not a defining feature, nor unique. In fact, one defining feature of SPAs is the offline capabilities (service workers, caching, etc.), which sits at a bit of a tangent to database considerations like this.

If you can actually offload substantial CPU cycles to the client, yes, you'll save server costs. But the SPA hype has led to a lot of SPAs that work like this:

> User clicks a tab. A request to server fetches the JSON data for the tab. Client renders it to HTML. User fills in some fields and clicks submit. A request to server sends the JSON form data and gets a JSON response code. Client shows a confirmation screen. ...

In this case, you're not saving much by templating JSON on the server instead of just templating HTML.

This was one of the appeals initially, and would certainly still be true if you were doing something very processor intensive that could securely be done on the client.

Languages/runtimes have gotten faster and more optimized, while hardware has continued to move forward. It's also far easier now to add more backend instances using orchestrators like k8s, so it's less of a big deal to have to add replicas.

> Can server costs be reduced by offloading the work to the front end?

I would say yes. One significant benefit of SPAs is that you can produce fairly complex applications without any server logic, only static hosting. The workload is essentially offloaded to the build process and the front-end. You still need to carefully consider the effect on e.g low powered and js-disabled devices ... but these are straightforward considerations.

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