1.3 IaaS, PaaS, SaaS and serverless
You can place any product on the responsibility spectrum and say who patches what.
Before:00. Groundwork — Linux, Networking & GitUnlocks:02. Compute09. Cost Engineering
IaaS, PaaS, SaaS and serverless are points on one spectrum of responsibility, and this topic teaches placing any product on it and saying who patches what. It sits at the centre of the foundations because the placement decides cost, effort and risk for everything built later. The common confusion is treating serverless as magic; it is a billing model — pay per invocation, give up control of the machine — and the trade reads the same as every other move up the stack: less to manage, less you can decide.
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The four models with a real example of each
Infrastructure, platform, software and functions are four points on one spectrum of how much you operate yourself. Attaching a real product to each name is what makes the spectrum stick.
What you give up as you move up the stack
Moving up the stack you give away control in exchange for work you no longer do, and the thing you give away is usually the thing you need on the day something goes wrong. Naming that trade in advance is the point of this item.
Serverless as a billing model, not a magic trick
Serverless does not mean no servers; it means someone else operates them and you are billed per request rather than per hour. Treating it as a billing arrangement rather than magic keeps expectations sane.
Choosing a model for a given team's size and skills
The right model depends on how many people you have and what they already know, not on which tier is most advanced. A small team running managed services well beats the same team running infrastructure badly.
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