AppendQueueOptions

How a PartitionAppendQueue groups appends: the most appends one partition's EventLog.appendAll takes (maxBatch). The queue is always on, for every backend (measured 2026-10-23): a group is one statement on PostgreSQL and one insertMany per collection on MongoDB, which carry more under load than single appends and cost a few per cent at low concurrency. These are the backends' constants, not settings.

A log that takes several partitions at once (EventLog.appendsAcrossPartitions) gets the partitions' groups merged: mergers committers, each taking what the partitions handed it meanwhile, at most mergeMax streams, into one call; a log that does not take them is called per partition.

Fields may be added: Wow builds it from the host's configuration, so the constructor is internal to Wow.