Improve performance ruby app PDF generation

Hi, We have an existent RoR project that involves the generation of PDF files based on a lot of logic operations, here the problems : - Results controller needs a lot of improvement, there is a lot of DRY , and probably VERY unefficient code. With few records works like a charm, but with real testing data generating takes a lot of time, and I'm having time outs and server crashes because is taking too much time /resources. First point is to reduce the generating times and solve all that errors. - I'm not sure if I would be able to proccess everything "on the fly" with concurrent clients, so probably we need to implement sidekiq and create a queue for each user to see actual generating pdfs, here I need your opinion. Second point is about managing resources/tasks/threads with concurrent client users generating pdf reports. Users CAN NOT be waiting 30-40 seconds with no loading screen or message, and server can not time out or crash. System is about evaluations for students , so an evaluation has many questions, question has many attributes of different types, school has grades that has many students and so on, so now you can imagine what happens when I have an evaluation with 40 questions (each question has a lot of data related) , and 40 students (40 students x 40 answers, TONS OF DATA). I'm actually dont saving PDFs but generating files on the fly, please attach creative solutions, we want to avoid having gigs and gigs of reports because are used by clients once a year. PLEASE!! DONT COPY PASTE YOUR INITIAL SPEECH, just attach relevant data and portfolio. I will be hiring people who really understands and write me with a solution and not the typical "I can do anything". If the freelancer can finish this work good theres more work availible about this project. Regards and feel free to ask about anything.