As part of our commitment to building software that’s secure by design, we rigorously evaluate not just what our applications do, but how they communicate. In today’s architectures, API design choices can significantly impact security posture. With our latest software release on the horizon, it’s time to shed light on a pivotal decision: gRPC vs REST API, and why gRPC aligns better with our secure design principles.

Understanding the Basics

Feature	REST	gRPC
Protocol	HTTP/1.1	HTTP/2
Data Format	JSON (text-based)	Protobuf (binary format)
Performance	Slower due to text parsing	Faster due to binary streaming
Language Support	Broad	Broad, with official tooling
Security	TLS, OAuth, and headers	TLS, mTLS, and token-based auth

REST is battle-tested and widely adopted, relying on JSON over HTTP. It’s human-readable and excellent for public-facing APIs. But when privacy, integrity, and performance are paramount, REST begins to show its age.

Why gRPC Is More Secure by Design

gRPC was built with security and performance in mind, key qualities that resonate with our development philosophy. Here’s how it shines:

• Efficient Binary Serialization: gRPC uses Protocol Buffers, which are not only compact but harder to intercept and manipulate compared to plain-text JSON.
• TLS: gRPC uses TLS to provide secure connections, enforcing encryption and reducing the risk of man-in-the-middle attacks.
• Mutual TLS (mTLS): For sensitive inter-service communication, gRPC makes implementing mTLS more straightforward, adding strong identity verification for both client and server.
• Smaller Attack Surface: Fewer exposed endpoints and streamlined transport mechanisms reduce surface area for exploitation.
• Strict Schema Enforcement: With Protobuf, contracts between services are strictly typed and versioned, thus eliminating ambiguity and tightening validation.

 Conclusion: Why We Choose gRPC While REST remains a robust and flexible option for many use cases, we’ve opted for gRPC as our default API approach where trust, speed, and security matter most. It aligns with our Secure by Design mantra, offering encrypted communication, strong identity verification, and a reduced attack surface. BTW we use gRPC with TLS for both internal and external communications.