At a glance
Connections In Use is the number of client connections currently open against your MongoDB deployment, read live from serverStatus().connections.current. It is the raw capacity heartbeat: how many sockets your application servers, workers, and tools are holding right now. Read it alongside the available headroom to know how close you are to the connection ceiling before refusals start.
What it tracks
The card reportsconnections.current from db.serverStatus(), the count of incoming connections open at the moment of the poll. This includes connections from your application pools, background workers, replica-set heartbeat traffic, and any interactive mongosh or tooling sessions. The time window is RT (real-time), so the value refreshes on each poll and reflects the present state rather than an average.
Read it against its companion, connections.available, which is the remaining headroom before the server’s maxIncomingConnections ceiling. When current climbs and available shrinks toward zero, you are approaching the point where new clients get refused. This card has no alert threshold of its own (it is a capacity gauge, not an alarm), but it is the denominator behind Connection Pool Saturation %, which does alert at 90%. Pair the two: this card tells you the absolute count, saturation tells you how full the tank is, and Connection Errors (24h) tells you when the tank overflowed.
Reconciling against the source
Rundb.serverStatus().connections.current in mongosh against the node, or read the Connections chart in the Atlas Metrics tab. Our value is a per-poll snapshot aligned to your reporting time zone, so a brief spike between polls may not appear; check current plus available together to confirm headroom.