How do you manage the pressure of delivering a great performance on a tight schedule or with minimal rehearsal time?

I try to do my homework at home  when hired to do a show with no rehearsal scheduled, I play the songs at home many times, until I really got them under my fingers.

If reading is not allowed onstage then I'll memorize everything I can playing the stuff in repeat mode until it comes really natural, otherwiswe I'll bring the notation with me but even in this case I'll rehearse everything at home to check difficult moments, unison etc...I don't want last minute surprises!

Even if there's little time between the calling and the gig, keeping a balanced and positive attitude will help you to get the best of every situation...that said, my suggestion is to keep yourself prepared practicing the right amount of time in the quiet  moments, so you'll be confident when a sudden gig call comes.

You can only do the best you can do.

Be transparent with any and everyone around you and do the best you can do. Anything beyond that will only hinder your ability as a creative and cause further problems. Don't stretch yourself too thin, and remember to take breaks. You got this.

Good mindset - organization - enough sleep - motivation. If the head is in the game, these pressured sessions are a great challenge because you can be so efficient and productive. Finishing a piece in time makes it a great act of defiance. Think positive and know your talent. Don't trigger your mindset with phrases like "I can't do this." Start your day right and healthy, take breaks but calculate them right and set the time where you want to be really done.
It's the best feeling ever checking off the To-Do list after such performance. 

Handling the pressure of delivering a great performance within tight deadlines requires being highly organized and efficient. Fortunately, today we have tools that allow us to record multiple takes, select the best parts, and even combine them quickly and accurately. My last two years of recording custom bass tracks on Fiverr have provided me with the know-how to work effectively within tight timeframes.

First of all, it helps a lot to have a deep knowledge of different musical styles, so that I can transfer the approach of similar works studied in the past to the current project. If I have to arrange a piece that seeks to recreate 19th century romanticism, since I know it so well, it is quick to offer a pro performance because I apply what I already know of so many composers of that century, whereas if I didn't know them, it would be impossible to do it almost immediately.

Secondly, since I work as an interpreter of my own arrangements, it is important to have good improvisational skills, something I have cultivated for years and which I apply to all kinds of styles. Improvisation is usually associated with jazz, but it can be applied to any style. That added to a theoretical knowledge of the styles and a good interpretative ability to immerse myself in the emotionality of the work, allows me a quick response capacity. In 2022 I won an international piano composition competition and although I had some preparation sessions, it was basically a work of improvisation. It was not months composing that piece, but less than two weeks. I rely more on my intuition and "letting myself go" than on intellectual or theoretical overthinking when I make music.

I think the best way to get a good result is to be organized down to the smallest detail.

When I don't have a big workload, I create some default sessions, templates, so I can cut the project creation time in the moments of maximum work.

Furthermore, I focus on one job at a time, trying to avoid useless moments of multitasking that a human brain can hardly manage.

I focus 100% on the work I have to do, also taking advantage of the various time zones of the clients.

I specialize in drum sessions on Fiverr, and one of the things that makes it really easy to learn songs in a very short time is to always have my kid set up my up and ready to go all the time. I also have an electronic kit set up at all times so that I can use it to practice the song before I go and jump on the actual acoustic for the recording. This way, I can build some muscle memory very quickly and be more efficient to record. I also have all my effects and mixing template set up, to work as quickly as possible, providing the best results. 

I've been working on Fiverr for 4 years now and delivered over 500 orders.
During these years I developed a work routine that allows me to have many hours a day to work on Fiverr orders and, since I have a home studio, I'm always ready to work whenever is needed.