When acquiring a large amount of users both mysql and sqlite show their true power. They are slow and will soon be outdated with my experience. People are switching to Redis to handle the caching and dbs like mongodb to store the data. All I ask for is MongoDB. This would allow multiple connections and allow a much quicker and more enjoyable experience for users. Especially those with a high amount of concurrent users or those who require concurrent connections to the database. Thank you for your time and all the support you offer.
Personally, with my experience in RDBMS I am pretty sure they will not be outdated. I have not heard Google removing SQLite from their Android API (it still exists even in P). I also have not heard from friends at Oracle that MySQL or Oracle RDBMS are being shelved anytime soon.
Mongo and Redis are great for document stores but, for data integrity and 20+ years of relational database design, SQLite3 and MySQL do what is needed in PhantomBot which is a key/value and key/secondary key/value store. In terms of data integrity, I read that Mongo was beta testing ACID in February, interestingly, something built into RDBMS for decades. What this may illustrate is that people are using Mongo and not happy with the data consistency and integrity options provided. The idea that they are looking to use transactions and finally supporting multi-document transactions that are part of the power of RDBMS speaks volumes to me.
I have used both, and use both at work. At least, we use MySQL and DynamoDB. We find that Dynamo is a good database for specific cases just as MySQL is. It just depends on your use case and architecture as well as support options.
Finally in terms of performance. While I cannot speak to MySQL and PhantomBot as we provided the option and it plugged in easily to our architecture, I do not use it. We have tuned SQLite3 though to be very efficient and have tested it in 5,000+ viewer channels and it performs quite well.