Service Discovery Calculator

Size a service registry: heartbeat rate, watch notification fan-out and registry memory footprint.

About Service Discovery Calculator

A registry's steady-state load is liveness traffic — every instance checks in once per interval — while its bursty load is watch fan-out, where one instance change notifies every watcher of that service. Memory scales linearly with instance count. Registries like Consul and etcd are consensus-backed, so every heartbeat is a replicated write; halving the heartbeat interval doubles the write rate against a quorum that has a hard ceiling.

Formulas

Service Discovery

heartbeat rate = registered instances ÷ heartbeat interval, where instances = services × instances per service.

instances: Total registered service instances
heartbeat interval: Seconds between liveness updates
heartbeat rate: Sustained writes the registry must absorb

Watch fan-out

watch notifications = churn per second × watchers per service

churn per second: Instances registering or deregistering each second
watchers: Clients subscribed to each service's endpoint list

Worked example

With the default values below, Service Discovery Calculator returns Heartbeat Rate of 240.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Registered servicesminimum 1 services: 400 services
Instances per serviceminimum 1 instances: 6 instances
Heartbeat intervalminimum 0.1 s: 10 s
Instance churn per minuteaccepts 0–100 %: 2 %
Watchers per serviceminimum 0 watchers: 8 watchers
Registry bytes per instanceminimum 32 bytes: 512 bytes

Results

Heartbeat Rate: 240.0 requests/s
Registered Instances: 2,400
Watch Notifications: 6.40 events/s
Registry Memory: 1 MiB
Total Registry Write Rate: 240.8 writes/s

Step by step

1Values used
2Service Discovery
3Watch fan-out
4Heartbeat Rate= 240.0 requests/s
5Registered Instances= 2,400
6Watch Notifications= 6.40 events/s
7Registry Memory= 1,228,800
8Total Registry Write Rate= 240.8 writes/s

Assumptions and limits

The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Service Discovery calculated?

heartbeat rate = registered instances ÷ heartbeat interval, where instances = services × instances per service. A registry's steady-state load is liveness traffic — every instance checks in once per interval — while its bursty load is watch fan-out, where one instance change notifies every watcher of that service. Memory scales linearly with instance count.

Why does Service Discovery matter?

Registries like Consul and etcd are consensus-backed, so every heartbeat is a replicated write; halving the heartbeat interval doubles the write rate against a quorum that has a hard ceiling.

What values do I need to enter?

This calculator takes 6 inputs: Registered services, Instances per service, Heartbeat interval, Instance churn per minute, Watchers per service, Registry bytes per instance. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.