RPC vs REST: Choosing the Right API Architecture
REST and RPC are two different approaches to designing application programming interfaces. Neither replaces the other. The best choice depends on the communication patterns, client requirements, system boundaries, and long-term maintenance goals.
Table of Contents
- 1. What is REST?
- 2. What is RPC?
- 3. Philosophy Differences
- 4. API Naming and Design
- 5. Performance Considerations
- 6. Developer Experience
- 7. Security Practices
- 8. When REST Makes Sense
- 9. When RPC Makes Sense
- 10. Hybrid Architectures
- 11. Real Projects
- 12. Decision Framework
- 13. Common Mistakes
- 14. Lessons We've Learned
- 15. Frequently Asked Questions
1. What is REST?
Representational State Transfer (REST) is a **resource-oriented architectural style**. REST designs treat data as entities (resources) exposed via unique URL paths. State updates are executed using standard HTTP verbs (GET, POST, PUT, DELETE). REST is stateless, utilizes built-in HTTP status codes (200, 201, 400, 404, 500) to describe outcomes, and relies heavily on caching protocols.
2. What is RPC?
Remote Procedure Call (RPC) is an **action-oriented protocol**. RPC allows an application process to execute functions (procedures) on a remote server as if they were local code calls. Instead of exposing database entities directly, RPC interfaces expose actions (e.g. `calculateInvoice`, `sendNotification`). RPC implementations (like gRPC or JSON-RPC) execute requests via simple POST methods, sending payload data in binary formats (Protobuf) or JSON schemas.
3. Philosophy Differences
The core difference lies in how communication models conceptualize data operations:
Resource-Oriented (REST)
Focuses on *nouns*. Objects exist at persistent paths (e.g. `/salons/1`). Standard CRUD verbs modify the resource state. The server describes resources, decoupling client navigation from direct server functions.
Action-Oriented (RPC)
Focuses on *verbs*. Systems trigger remote commands directly (e.g. `salon.checkInClient`). The network behaves as an execution pipeline, passing function inputs and receiving function results.
4. API Naming and Design
Nouns and verbs dictate how you specify interface layouts:
| Operation | REST Style | RPC Style |
|---|---|---|
| Fetch Records | `GET /customers/123` | `POST /rpc/CustomerService.GetCustomer` |
| Update Values | `PATCH /customers/123` (payload) | `POST /rpc/CustomerService.UpdateEmail` (payload) |
| Trigger Actions | `POST /customers/123/activate` | `POST /rpc/CustomerService.ActivateCustomer` |
| Delete Entities | `DELETE /customers/123` | `POST /rpc/CustomerService.DeleteCustomer` |
5. Performance Considerations
Compare data formats and cache structures to estimate latency:
Serialization & Size: REST APIs default to JSON payload structures, which are readable but introduce parsing latency. RPC protocols (like gRPC) utilize binary serialization (Protobuf). Binary payloads remove serialization overhead, reducing packet volumes by up to 50%.
HTTP Caching Boundaries: REST GET requests are natively cached by HTTP intermediaries (browsers, CDNs, proxies). RPC POST methods are bypass-cached by default, requiring you to construct custom caching logic inside application layers.
HTTP CACHING COMPARISON
Client → [ GET /salons/1 ] → (CDN Cache Hit) → Return JSON instantly
Client → [ POST /rpc/GetSalon ] → (Bypass Cache) → Execute server-side DB query
6. Developer Experience
Maintain client integrations using explicit documentation schemas:
- REST Documentation We write OpenAPI v3 specs to describe REST routes. OpenAPI compiles to interactive documentation, allowing clients to test endpoints in browsers.
- RPC Documentation gRPC requires defining Protobuf files (`.proto`). The Protobuf compiler (`protoc`) automatically generates typed client libraries in Go, TypeScript, Java, and Python.
7. Security Practices
We apply standard security layers across both interface patterns:
Stateless JWT Validation: Authentication checks are run at the gateway boundary, parsing JSON Web Tokens (JWT) to bind user and tenant contexts.
Idempotency Checks: We validate unique request hashes on write actions, preventing duplicate database entries when clients retry failed calls.
8. When REST Makes Sense
REST is our default choice for external-facing systems:
- • **Public Developers Integrations:** Third-party integrations require standard HTTP paths and easily readable JSON formats.
- • **Edge CDN Caching:** Content-heavy sites and product catalogs where assets are cached globally.
- • **Browser Client Communications:** Web client applications that consume standard browser fetch APIs.
9. When RPC Makes Sense
RPC is our preferred pattern for internal systems:
- • **Microservice Communication:** Internal server-to-server calls where type-safety and low serialization overhead are mandatory.
- • **Realtime Command Actions:** Applications triggering complex server operations (e.g. `restartPod`, `chargeCard`).
- • **Background Job Synchronization:** Queue worker processes running high-frequency data transformations.
10. Hybrid Architectures
Modern production systems frequently deploy both patterns. A B2B SaaS platform might expose **REST APIs** publicly for client web integrations, while using **gRPC** internally to coordinate high-speed communication between backend microservices. Using both patterns maps specific data requirements to the appropriate API style.
11. Real Projects
We apply these design principles across our production platforms:
BarberBase: Supabase RPC encapsulation
BarberBase is a salon operations platform. While SvelteKit routes render frontend layouts, we encapsulate scheduling operations (like booking client slots) inside Supabase RPC database functions. This ensures multi-user queue updates are validated atomically within Postgres database locks, preventing scheduling conflicts.
Read BarberBase Case Study ↗Bhejna: OpenAPI REST Interface
Bhejna is a messaging gateway that queues WhatsApp payloads. Because Bhejna integrates with external application webhooks, we designed its public endpoints as standard REST paths specified using OpenAPI v3 contracts. This allows third-party client systems to execute integration calls securely using standard HTTP clients.
Read Bhejna Case Study ↗12. Decision Framework
We evaluate API architectures using four technical constraints:
| Operational Requirement | REST Style | RPC Style | Recommended Choice |
|---|---|---|---|
| Third-Party Developers Access | Universally supported JSON paths. | Requires importing custom Protobuf schemas. | REST |
| High-Frequency Microservices | JSON parser overhead, HTTP routing logs. | Low serialization binary payloads (gRPC). | RPC |
| Global Edge Caching | Native HTTP GET caching on CDNs. | POST requests bypass edge caching. | REST |
| Type-Safe Client Libraries | Depends on third-party OpenAPI generators. | Generated directly from `.proto` definitions. | RPC |
13. Common Mistakes
Verb-Heavy REST Paths
Creating REST paths like `POST /customers/123/updateEmailAddress`. In REST, actions should modify resource properties: `PATCH /customers/123` with email in the body. If you require action-specific routing, select RPC instead.
Over-versioning APIs
Creating new version subfolders (e.g. `/v2/`) for minor database schema updates. We recommend additive changes (adding optional fields) to preserve backward compatibility.
Over-engineered Internal RPC
Deploying complex gRPC configurations for simple frontend dashboards. A lightweight REST endpoint often provides faster developer velocity than managing Protobuf compilations.
Ignoring POST Caching Limits
Using RPC POST actions to fetch static resources. This prevents browser caching, increasing database read queries under load.
14. Lessons We've Learned
Our API design choices are based on production experiences:
- Contract-first design prevents interface bugs Specifying OpenAPI contracts before writing code ensures our client and backend models map parameters accurately.
- Custom RPC handles complex transactions While REST handles CRUD actions cleanly, executing multi-table operations (like calculating pricing rules during checkout) is more performant when encapsulated as an RPC.
15. Frequently Asked Questions
What is the main difference between REST and RPC?
REST is resource-oriented, organizing data around nouns (endpoints like `/customers/123`). RPC is action-oriented, organizing data around verbs (function calls like `CustomerService.UpdateEmail`).
Is RPC faster than REST?
RPC implementations (like gRPC) are generally faster than REST because they use binary serialization (Protobuf) and persistent HTTP/2 connections, reducing payload size and connection latency.
Can REST APIs support realtime data?
REST is stateless and not designed for persistent connections. Real-time updates require layering protocols like WebSockets, Server-Sent Events (SSE), or Webhook callbacks.
Why is REST preferred for public APIs?
Because REST uses standard HTTP protocols and JSON payload formats. This allows external developers to integrate with endpoints easily using standard browser tools without importing proprietary SDK schemas.
What is gRPC?
gRPC is a high-performance RPC framework developed by Google. It uses Protobuf for data serialization and HTTP/2 for transport, making it ideal for microservice communication.
How does HTTP caching affect REST?
REST GET requests can be cached by browsers, proxy servers, and edge CDNs, allowing duplicate read queries to be resolved instantly without hitting your backend database.
Why does RPC bypass HTTP caching?
RPC executes operations using POST methods, which are designed for mutating states and are not cached by default by browsers or edge networks.
What is OpenAPI?
OpenAPI is a schema specification standard for describing REST APIs. It defines paths, request payloads, and response statuses to enforce strict integration contracts.
Can I use both REST and RPC in the same project?
Yes, many production systems deploy hybrid designs. Internal microservice pools use RPC for high-speed communication, while public client portals expose REST gateways for third-party integrations.
How does RPC handle API versioning?
gRPC handles versioning by package names in Protobuf schemas. In JSON-RPC, version tags are passed in the request body or version paths.
How do you handle validation in contract-first design?
Validation is defined inside the OpenAPI contract or Protobuf schemas. Incoming requests are validated against these schemas on the server side before code execution.
What is idempotency in APIs?
Idempotency ensures that making duplicate requests with the same payload (e.g. due to connection retries) only executes database changes once, preventing duplicate records.
Why is REST stateless?
REST is stateless because every request must contain all credentials and parameters required for execution. This allows edge routers to scale horizontally without relying on shared session state stores.
What is the advantage of binary serialization?
Binary formats (like Protobuf) serialize variables directly into compact byte arrays, bypassing text parsing, reducing payload size and CPU usage.
How do you test RPC interfaces?
We test RPC APIs using schema-aware client tools (like Postman or gRPCurl) that parse Protobuf schemas to generate request payloads.
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