I am looking at LS as a contender for a survey I need to run. My question is what is the scalability or load that LS can handle. I understand that much of this question resides on the environment that it resides but if you can shed any light from the projects perspective that would be helpful.

Specifically I am planning on sending out a mass email to 100,000+ of my customers to take a survey. I am interested if LS can support this potential spike/load.

Thanks for any input.

First of all it is common practice NOT to send out all emails at once, but in smaller portions. This is not only something you should do for Limesurvey, but this is generally a common practice with survey invitations.

Because once you send out the email, chances are high that many will at least click on the link, even if it is just curiosity.

Limesurvey can handle the responses of 100.000 respondents (but I'd rather say the response rate will be below 5% anyway).

Your main problem will be the concurrent users (users that are in the survey at the same time), which might create a high load on your server.

There is a whole thread about scaling limesurvey and I think there is also some information in the manual.

As you already said, this depends very much on your server environment but also on the survey itself. A short and simple survey (without many conditions) might handle a far higher number of respondents as a long survey with many questions and many conditions.