Throttling back

You should be prepared for some initial loss in average team productivity each time a new pair is added. You may not see an overall increase in velocity when you first add new pairs. This is normal as the new pair adapts to the new processes and the team "re-gels". Sometimes you may have an iteration where you actually see a decreasing overall velocity. Pay attention to these yellow flags and try to see if there is a single cause for the decline, or just alignment of the planets. If a decline becomes a trend, it may indicate that infrastructure or processes must be scaled up to handle a larger team or more complex software. Either way, if the velocity trend is downward, it would be a good idea not to add any more pairs until you see a shift in a positive direction.