Everything works reasonably well in a relational database if your data is small. As you scale up, the performance will fall off a cliff for any data model that

Everything works reasonably well in a relational database if your data is small. As you scale up, the performance will fall off a cliff for any data model that the internals of the database kernel were not specifically designed for. No relational database kernel is optimized for time-series data models, so poor performance is just a matter of scale.