Do you think about data security while developing your products? Which tool/Services to avoid getting your user's data leaked/ hacked?
Yes! I think it's one of the most important parts. Users trust you with their data. I don't use any tool but I write tests for critical parts of the applications :). There's also a lot of good practices to make programs more secure. I use OWASP Top 10 as one of my references, you can find it here: https://www.owasp.org/index.php/Top_10-2017_Top_10
SSL + Devise (Rails) or just encrypt every message my users send, so even if a hacker got access to my DB he will just obtain a bunch of hashes with nonsense.
For e-mails, I just recollect all the emails send it directly to my MailChimp/Mailgun marketing list so when this arrives at my DB all of them are already encrypted. So no data to disclose.
I know that I could be making my app safe if I invest time in developing some security measures, but in the end, unless you are delivering for a big company or a hot startup, you should be shipping a better product instead of doing backend work.
I always use community libs for auth and password storage, so I don't have to implement my own logic.
Servers have some firewall rules and auth is only via ssh keys.
Let's encrypt on every domain, always.
Above everything, I
never store sensitive data that isn't needed.