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Remote procedure call

Definition

A remote procedure call (RPC) is a way for a program to request execution of an operation in another process, often on another computer, through an interface resembling a procedure or method call. The caller supplies inputs and receives results or an error. Communication crosses a process or network boundary, so delays and partial failures make RPC behavior different from an ordinary local call.

What it means

A client might ask another service to calculate a result, retrieve an item or submit a job. RPC frameworks handle much of the message exchange and data encoding, allowing developers to work with named operations. That convenience does not erase the distributed-system boundary. A timeout may mean the server never received the request, is still working or completed the operation but the reply was lost. The application must account for that uncertainty.

How it works

A service defines available operations and input and output structures. Client-side code encodes a request and sends it through the chosen transport. Server-side code decodes the request, invokes the operation and returns a response. Frameworks may provide generated bindings, authentication, deadlines and streaming. RPC is the broader pattern; technologies such as gRPC and the protocol specified in RFC 5531 are particular implementations. Their message formats and guarantees are not interchangeable.

Three practical examples

• A web application calls an internal catalog service to obtain product details.
• An AI application calls a model-serving process to request an inference result.
• A workflow coordinator submits a processing job to a worker service and receives an acknowledgment or operation identifier.

Think of it this way

Think of asking a colleague in another office to perform a task and return the answer. The request can be clear even though delivery and response take time. The analogy is limited because software may retry automatically, messages may be duplicated and the caller may not know whether the work happened. A familiar method-call syntax can hide those possibilities unless the design exposes them.

Worked example

Suppose a client sends CreateJob with request identifier R17. The server creates job J42, but the response is lost. The client reaches its deadline and retries. Without a deduplication rule, the server might create J43 as well. With an appropriately implemented idempotency mechanism keyed by R17, the server can recognize the repeated request and return the existing result. The example shows why a retry is not automatically harmless. It does not claim that every RPC framework supplies this application-level behavior or that simply adding an identifier field makes it correct.

Illustrative case study

In a fictional company, Birch Analytics introduces an RPC interface for launching evaluation jobs. Early tests handle normal responses but not interrupted connections. The team adds explicit request identities, bounded deadlines and a way to query job status after an uncertain response. It tests repeated requests and records operation outcomes. The case illustrates designing for partial failure, without promising that the transport guarantees exactly-once business execution under all failures.

Common misconceptions and mistakes

RPC is not equivalent to a local function call in latency or failure behavior. A successful network connection does not prove the remote operation completed. A timeout does not prove it did not complete. Retrying every error can overload a struggling service or duplicate side effects. RPC also does not imply one universal protocol, synchronous execution or a single request and response message; some frameworks support asynchronous and streaming interactions. Authentication and authorization must be configured for the actual service.

Business use

Use RPC when clearly defined service operations fit the application's boundaries. Keep interfaces versionable and document which operations are safe to retry. Choose deadlines based on service objectives and measured behavior, then consider how a chain of calls shares the overall time budget. For AI inference, distinguish model processing time from queuing and communication delays. Monitor errors and retries together so repeated attempts do not conceal instability. Avoid extremely chatty designs that turn many tiny local-looking calls into costly network round trips.

People also ask

Must an RPC cross the internet?

No. It can connect processes on the same machine or within a private network.

Is gRPC the same as RPC?

gRPC is one framework implementing the broader remote-call approach.

Does canceling a call undo completed server work?

Not automatically. Cancellation signals loss of interest or termination according to the framework, while application side effects require their own handling.

Check your understanding

A client times out after asking a server to create an order. Is it safe to assume no order exists?

Answer: No. The operation may have completed before the response was lost or delayed. The application needs a documented way to determine the outcome and retry safely if appropriate.

Related terms

• Client-Server Architecture
• API
• serialization
• deadline
• idempotency
• retry
• gRPC

Learn next

Trace a request through three cases: success, failure before execution and lost response after execution. Decide what the client can actually know in each case. Then design a retry policy and status-check mechanism for an operation with side effects, rather than relying on local-call intuition.

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Sources

Sources: RFC Editor, “RPC: Remote Procedure Call Protocol Specification Version 2,” RFC 5531, https://www.rfc-editor.org/info/rfc5531/; gRPC, “Core concepts, architecture and lifecycle,” https://grpc.io/docs/what-is-grpc/core-concepts/; gRPC, “Retry,” https://grpc.io/docs/guides/retry/; gRPC, “Cancellation,” https://grpc.io/docs/guides/cancellation/. Primary standards and project documentation search excerpts consulted; full protocol-specific and editorial review remain pending. The job example describes an application design requirement, not an automatic framework guarantee.

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