The word period (mainly used in the US English) means the discussion is over and you emphasize that what you said is final (from your side)
However, I'm not sure whether the placement of the word 'period' looks natural in the sentence in concern.
Cambridge Dictionary defines it:
[mainly US] said at the end of a statement to show that you believe you have said all there is to say on a subject and you are not going to discuss it any more
The example follows:
here will be no more shouting, period!
Even I speak that word in the recommended way, at the end of the sentence meaning final (at least from my side).
But here, the sentence has period in the middle of the sentence, which makes less sense to me. I had hard time finding such example sentence from standard sources. I'll be happy to see if someone comes up.
If you ask me, I'd suggest 'comma' there over a 'period'.
In addition to making sure that things work, the most important consideration when you’re building applications is making sure that they’re easy to maintain.
In addition to making sure that things work, period, the most important consideration when you’re building applications is making sure that they’re easy to maintain.
In fact, this is really a strange usage of period word (in between commas) I've ever seen! :)