Philly ETE 2023 — REPLs All The Way Up: A Rubric For Virtuous Feedback Loops — Avdi Grimm & Jessica Kerr



We all know that the key to successful software development is iteration and feedback loops, whether that takes the form of the red-green-refactor cycle, or agile project planning. But not all feedback is equally valuable. How do you know if you’re poised to spin gold or just spin in circles?

We propose a novel archetype for virtuous feedback cycles: the humble Read-Eval-Print-Loop (REPL). We’ll talk about the history of REPLs and how they revolutionized early programming environments. We’ll examine the evolution of iterative feedback in software development processes, through the lens of “REPL nature”. We’ll talk about “scientific” processes, and why the proverbial theory/experiment cycle is not sufficient for good science or graceful software development.

Finally, we’ll explore what makes for better feedback loops at every level of the software process, from building algorithms up to business intelligence. You’ll leave with a new rubric for evaluating and improving the iterative circles you work in every day.

About Jessica Kerr

Jessica Kerr is a symmathecist, in the medium of code. She believes in learning systems made of learning parts: enthusiastic people and evolving software. She is a Principal Developer Advocate at, where she teaches developers to make their software teach them what’s going on inside. In twenty years of professional software development, she has programmed in and spoken at conferences about Java, Scala, Clojure, TypeScript, Ruby, and Elm. She lives in St. Louis, MO with two children who invent worlds and draw characters with superpowers, and two cats who meow and knock over water glasses.

About Avdi Grimm

In the course of over twenty years of software development, Avdi has worked on everything from aerospace embedded systems to enterprise web applications. He’s a consulting pair-programmer, the author of several popular Ruby programming books, and a recipient of the Ruby Hero award. These days he invests his time helping other developers grow their programming practice at Graceful.Dev.

About the Conference

The Philly Emerging Technologies for the Enterprise (ETE) is the Mid-Atlantic’s premier developer’s conference. Entering its 17th year, we’ve brought world-class speakers — including some local favorites — to speak about leading-edge technologies being used today, and emerging technologies that will be important for attendees to know about in the near future.

Watch More

Check out our YouTube playlist to watch all the talks from Emerging Technologies for the Enterprise 2023.