Service Discovery Calculator

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

Inputs

Registered servicesservices

Instances per serviceinstances

Heartbeat intervals

Instance churn per minute%

Watchers per servicewatchers

Registry bytes per instancebytes

Heartbeat Rate

240.0requests/s

Registered Instances

2,400

Watch Notifications

6.40events/s

Registry Memory

1 MiB

Total Registry Write Rate

240.8writes/s

Step by step

Values used
Registered services = 400 services; Instances per service = 6 instances; Heartbeat interval = 10 s; Instance churn per minute = 2 %; Watchers per service = 8 watchers; Registry bytes per instance = 512 bytes
Service Discovery
heartbeat rate = registered instances ÷ heartbeat interval, where instances = services × instances per service.
Watch fan-out
watch notifications = churn per second × watchers per service
Heartbeat Rate
= 240.0 requests/s
Registered Instances
= 2,400
Watch Notifications
= 6.40 events/s
Registry Memory
= 1,228,800
Total Registry Write Rate
= 240.8 writes/s

How it works

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

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.

You might also need

mDNS Calculator DNS Cache Calculator Active Directory Replication Calculator