Epoch fields

An epoch groups an inventory with the deltas and monitor rows that followed it.

Field	Type	Unit	Meaning
sparklogs.epoch.id	string		This era's opaque id. Globally unique, so an equality query on it is meaningful across a whole fleet.
sparklogs.epoch.prev_id	string		The previous era of this agent and topic, so any row hands a consumer the one before it with no round trip. Absent for the genuinely first era, and after the agent's stored state was wiped.
sparklogs.epoch.seq	integer	count	A counter per agent and topic, starting at 1, so the last few eras are one range query rather than a walk. It can repeat across a crash, so it orders eras and never identifies one: that is what the id is for.