FAQs on supported protocols
The AWS Compute Optimizer and AWS Cost Optimization Hub services are adding SDK support for the
Smithy RPC v2 CBOR
What are the AWS JSON and Smithy RPC v2 CBOR protocols, and how do they differ?
A wire protocol acts as a mediator between a client and the service. The AWS SDK handles the serialization (converting an object to the wire format) and deserialization (converting the wire format back to an object) between the client and server transparently for both protocols.
AWS JSON - JSON is one of the most widely used and accepted data formats for communication between systems. This service uses AWS JSON as a medium to communicate between an AWS SDK client and the server. An HTTP request for a service API operation accepts input in the form of JSON, the operation is executed, and the response is returned to the SDK client in the form of JSON.
Smithy RPC v2 CBOR - Smithy
RPC v2 CBOR (Concise Binary Object Representation) is a
protocol developed by Amazon for more efficient data
transmission. It is a data format designed to keep message
sizes compact and to allow the format to evolve without
requiring version negotiation between systems. The key
difference from AWS JSON is that AWS JSON uses
human-readable text (like {"name": "John"}),
while Smithy RPC v2 CBOR uses a binary format (sequences of
1s and 0s). This binary approach creates smaller data
packages that travel faster over the network and reduces
serialization time since computers process binary data
directly.
How do I get started with the Smithy RPC v2 CBOR protocol?
To get started, use the latest AWS SDK/CLI version to use the Smithy RPC v2 CBOR protocol for this service. The SDK will automatically use the Smithy RPC v2 CBOR protocol when available. Upgrade your AWS SDK to the specified version or any subsequent version.
Starting 2026-04-16, the following AWS SDKs will use the Smithy RPC v2 CBOR protocol, while the other SDKs will continue using the AWS JSON protocol:
AWS SDK for C++
AWS SDK for Go V2
AWS SDK for Java 2.x
AWS SDK for .NET v4
AWS Tools for PowerShell v5
AWS SDK for Swift
AWS SDK for Kotlin
What are the risks of enabling the Smithy RPC v2 CBOR protocol?
The added support of Smithy RPC v2 CBOR in the SDKs is expected to be fully transparent and effortless for customers. However, if you are using a custom implementation of the AWS SDK, or a combination of custom clients and the AWS SDK, that depends on AWS JSON-specific serialization behavior, it may be incompatible with the Smithy RPC v2 CBOR protocol.
What if my solution does not support Smithy RPC v2 CBOR?
To use the AWS JSON protocol, downgrade your SDK to a version released before 2026-04-16.
What AWS Regions support the Smithy RPC v2 CBOR protocol?
The Smithy RPC v2 CBOR protocol is supported in all AWS Regions where this service is available.
What latency improvements can I expect when upgrading to SDK versions that support Smithy RPC v2 CBOR?
Smithy RPC v2 CBOR provides up to 13% lower latency and up to 15% reduction in payload size compared to AWS JSON. The binary encoding eliminates the overhead of JSON text parsing and string escaping, which reduces both network transfer time and serialization cost.
Will the AWS JSON protocol be deprecated?
AWS JSON protocol will continue to be supported through older versions of SDKs. Also, some language-specific SDKs will continue using AWS JSON as it is more performant than Smithy RPC v2 CBOR due to the available JSON implementation for the language being faster than its CBOR implementation.
Where can I find more information about Smithy RPC v2 CBOR?
You can find more information about the AWS JSON protocol at
AWS JSON 1.0 protocol
