What's the longest you've heard back after a job?

[EnglishBrits]

Is 6 working days - 10 days after the interview too short?

Not a big company.

Internal job.

Not too short. I'd still have hope.

My first job out of university came about very oddly. I had applied for a job and didn't hear anything for 4 months. Then got a call one day from the owner of the business. They had hired someone else and it hadn't worked out. He then found my CV 'stuffed under his car seat' the night before he called me (he remembers reading it initially, but then lost it and forgot all about it), and decided to call me and see if I still was interested in the job.

I worked there for 2 years and absolutely loved it - it was the best start to my career I could have asked for.

Yes I would wait a couple more days before kindly following up, and try not to stress too much just yet. There are many reasons why it takes a while for hiring managers to get back to candidates after interviews: they may still have other candidates (internal and external) to meet in the first round of interviews, they may have a particularly busy week with lots of other priorities and deadlines, they may need approval from their own line manager, there's weekends/Bank Holidays/annual leave, or even just HR processes slowing every communication down.
Most of the time, it's not personal at all (even though, from the candidate's perspective, it always feels too long :)
Fingers crossed and good luck, I hope you get the job!