I kind of wish they wouldn't just hand out an A+ that easily. There are clear areas of improvement that the sub-scores call out (90 in both Key Exchange and Cipher Suite). They see the HSTS and grant the A+ when there is clearly improvement that can be made. In my mind, an A+ should be reserved for an SSL/TLS implementation that cannot reasonably be improved upon given the current state of the industry.

To improve your Key Exchange score you can bump your certificate from a 2048-bit key up to 4096-bit (giving you a score of 100). That's probably a good idea anyway as 2048 has been the minimum safe key size since 2010 [1], and I'd imagine that 4096 will become the new minimum over the next few years.

To improve your Cipher Suite score you can easily drop support for payload encryption with keys less than 256 bits in length. You will risk not supporting IE 6 users, but that's a fringe case these days (and there are many more issues with supporting IE 6 on top of that).

Making those adjustments, you should be able to get your scores to 100,95,100,100 which, in my opinion, is much more worthy of an A+.

There may be a few other tweaks you can make to improve items in the Protocol Details section, but I don't know enough about the node.js/io.js system to be able to recommend a clear path for improvement there.

The only score that you really would have difficulty bumping to 100 is the Protocol Support which is limited by the fact that all versions of IE prior to 11 had TLS 1.1 and 1.2 disabled by default. Unfortunately, there are still many IE 9 and 10 users out there

1. http://csrc.nist.gov/publications/nistpubs/800-131A/sp800-13...