Transducers – composable algorithmic transformation decoupled from input or output sources – are Clojure’s take on data transformation. In this talk we will look at what makes a transducer; push their composability to the limit chasing the panacea of building complex single-pass transformations out of reusable components (eg. calculating a bunch of descriptive statistics like sum, sum of squares, mean, variance, … in a single pass without resorting to a spaghetti ball fold); explore how the fact they are decoupled from input and output traversal opens up some interesting possibilities as they can be made to work in both online and batch settings; all drawing from practical examples of using Clojure to analize “awkward-size” data.