A student once asked me, half joking, whether a computer or a bored examiner decides her fate. Turns out the honest answer is both, just for different parts of the same exam.
The parts a machine checks
Reading, Use of English, and Listening are what Cambridge calls objective marking. There's a right answer and a wrong answer, nothing to interpret. For computer-based sittings, this gets checked automatically the moment you submit. For paper-based ones, the answer sheets get scanned and read the same way.
There's no judgment call here, which is exactly the point. A multiple-choice answer is either correct or it isn't, so there's nothing for a human to weigh in on.
The parts a person actually reads
Writing works completely differently. A trained examiner reads your response and scores it against specific criteria: content, organisation, language, communicative achievement. That's a judgment call every time, and Cambridge knows it, so the process around it is heavier than you'd expect.
Examiners go through a standardisation process before they're allowed to mark live scripts. Senior examiners mark a sample set first and agree on the standard. Everyone else practices against those same scripts until their marking lines up closely enough. Then, and only then, do they start marking real candidates, still under ongoing monitoring, with a senior examiner reviewing a sample of their work throughout.
Speaking is its own thing entirely. Two examiners assess you live, in the room, during the test itself, one running the conversation and one purely observing and scoring. It's not typically recorded, which means there's no re-check possible afterward the way there's for Writing. Both examiners have already been through the same rigorous training and monitoring, so the system leans on that upfront rather than a review after the fact.
Why the wait is so different depending on how you took it
Computer-based exams tend to come back in roughly two to three weeks. Machine-marked components are near instant, and Writing scripts get uploaded digitally, so examiners can start marking almost immediately rather than waiting for physical scripts to travel anywhere.
Paper-based sittings usually take four to six weeks. The scripts have to be collected, scanned or physically distributed to examiners, marked, then checked by senior examiners before anything gets finalised. None of those steps are instant, and there are a lot more of them.
There's also a category most people preparing for the FCE or CAE never think about: Young Learner exams. Those typically take around eight weeks, since the assessment there focuses on what a child could do rather than a strict pass or fail, and that kind of qualitative write-up takes longer to produce properly.
Do results ever come out early
This is the part I genuinely don't have a clean answer for, and I'd rather say that than make something up. Cambridge does sometimes release results in batches, with most candidates getting theirs first and a smaller group following within the next week or two, likely because a portion of scripts need extra checks before they're confirmed. Whether individual schools or exam centres see anything ahead of candidates isn't something Cambridge documents publicly in a way I could point you to with confidence, so take that possibility with a pinch of salt rather than as something to plan around.
What is reliable: you'll get an email the moment your specific results become available, so there's no need to keep refreshing a login page out of habit. Set a reminder for the general release window that applies to your exam type and let the notification do the rest.