> ## Documentation Index
> Fetch the complete documentation index at: https://docs.arupa.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Inter-service communication

> Choose how services share state and exchange messages.

Inter-service communication (ISC) lets services cooperate through
capabilities provided by the Arupa Kernel. Services do not need to share
memory or connect to each other's internal transports. The Kernel provides
the communication boundary and applies the same behavior to WASM and gRPC
services.

Choose the mechanism based on what you need to share:

* [KV storage](./isc-kv) provides shared in-memory state organized by
  namespace and key. Use it for values that other services may read or
  update later.
* [Service messages](./isc-message) provide synchronous, point-to-point
  request/response communication. Use them when one service needs another
  service to perform an operation immediately and return a result.

KV values are not durable and service messages are not queued or persisted.
If data must survive a Kernel restart, store it in a durable system outside
these ISC mechanisms. If a request must be delivered asynchronously or to
multiple services, define that behavior explicitly in your application
rather than assuming that the Kernel will queue or broadcast it.

Both mechanisms carry data across the service boundary through the generated
protocol bindings. Keep the data format and ownership rules clear between the
services that participate in the communication.