The author argued that the time series DBMSs don't need strict safety; People can endure losing some recently inserted data. And most of TSDB like InfluxDB allow flushing the data delayed, and people always want to do that.
VictoriaMetrics abandoned the WAL, and keep all the tables on the disk is consistent. So that the crash won't corrupt the data on the disk.
https://github.com/VictoriaMetrics/VictoriaMetrics
https://github.com/VictoriaMetrics/VictoriaMetrics/wiki
VictoriaMetrics
2018