Lambda Learner: Nearline learning on data streams

A common challenge for production machine learning systems is reacting to change. The world can change quickly, particularly on a social network. This can range from sweeping changes at the scale of the whole economy (like a pandemic) down to everyday occurrences, such as a dormant member returning to LinkedIn in search of a new job. It's typically not enough to train and deploy a model just once; we need to keep it fresh, while balancing model complexity, training time, and computational costs. Ideally, the instant new data becomes available, we would incorporate it into the model.