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For local MCP servers, use stdio; for remote deployments, use Streamable HTTP. The reported stdio-versus-remote-SSE measurements suggest a latency advantage for stdio in that test, but they do not establish a general performance ranking—and they are not evidence about current Streamable HTTP unless the tested protocol version is confirmed.
First, distinguish legacy SSE from Streamable HTTP
MCP uses JSON-RPC messages. With stdio, a client launches a local server as a subprocess, writes messages to its standard input, and reads responses from standard output. The server can write logs to standard error; standard output must contain valid MCP messages.
The older HTTP+SSE transport used HTTP endpoints for client-to-server messages and server-to-client event streaming. The specification dated March 26, 2025 says Streamable HTTP replaced that transport. Streamable HTTP uses an independently running server with HTTP POST and GET, and can use SSE for streaming. Compatibility support may still be needed for clients or servers built around legacy HTTP+SSE.
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The MCP maintainers’ December 19, 2025 transport roadmap describes stdio for local deployments and Streamable HTTP for remote deployments as the two official transports. That is guidance about intended use, not a measured performance result; custom transports remain possible for specialized requirements.
What the reported benchmark measured
A page published by World Programming Society on September 14, 2026, attributed on-page as “Originally by Storm,” says it benchmarked 10,000 tool executions. Its reported figures are claims by that page, not independently verified results:
Rank #2
| Measure | Stdio | Remote SSE |
|---|---|---|
| Mean invocation latency | 2.1 ms | 19.4 ms |
| p95 invocation latency | 3.8 ms | 32.1 ms |
| p99 invocation latency | 6.2 ms | 48.7 ms |
| Connection setup | 0 ms for a persistent pipe | 45 ms for TCP handshake plus TLS |
| Memory | Node.js worker: about 32 MB RSS per active process; Python FastMCP worker: about 21 MB RSS per process; compiled Go/Rust worker: under 7 MB RSS | Centralized daemon: about 42 MB shared across incoming streams |
The benchmark page does not provide enough visible detail about hardware, software versions, workload composition, network placement, concurrency, warmup, repetitions, measurement boundaries, or raw data to establish reproducibility. Its “Remote SSE” label also does not show that it tested the current Streamable HTTP format. The numbers therefore describe what that page reports, not a general result for MCP production systems.
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Which transport fits a production deployment?
Choose based on where the server runs and how it must scale, not on a single latency figure. The mechanics and SDK-specific operating characteristics differ:
| Decision | Stdio | HTTP transport |
|---|---|---|
| Deployment model | Client launches a local child process | Server runs independently and accepts HTTP client connections |
| Message flow | Standard input and output pipes | HTTP requests; streaming may use SSE |
| Backpressure | The C# SDK comparison describes implicit flow control through stdin/stdout | In that SDK, Streamable HTTP holds POST responses open; legacy SSE returns HTTP 202 before handler execution |
| Scaling and sessions | Process connection per client | In the C# SDK, stateless Streamable HTTP can scale without session affinity; stateful Streamable HTTP and legacy SSE require affinity |
| Server-initiated messages | Supported in the SDK comparison | Depends on HTTP mode; the SDK distinguishes stateless and stateful behavior |
| Security | Process-level trust boundary | Network-facing authentication and protections are needed |
The HTTP mode details in this table are specific to the MCP C# SDK transport guide, not a promise that every SDK behaves identically. Its ASP.NET Core integration uses stateless HTTP by default and disables legacy SSE by default. Check the documentation for the SDK and protocol version you deploy.
Protect network-facing MCP servers
The March 26, 2025 MCP transport specification tells HTTP implementers to validate the Origin header to help prevent DNS rebinding, bind local servers to loopback where applicable, and implement proper authentication. Without suitable protections, a malicious website could attempt to interact with a local MCP server through a user’s browser.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to benchmark the transport you will actually run
No independently reproducible, matched benchmark for stdio versus current Streamable HTTP is established by the sources cited here. To make a comparison relevant to your service, keep the workload and software fixed while testing the actual deployment modes:
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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitches- Name the protocol and implementation. Record the MCP specification revision, SDK and server versions, and whether the HTTP case is legacy HTTP+SSE or Streamable HTTP.
- Match the workload. Use the same tool operations, request and response sizes, concurrency, and server runtime for each transport.
- Measure the full path. Record connection setup separately from invocation latency, and include network placement, TLS, proxies, and any session or load-balancer behavior used in production.
- Test operational conditions. Measure sustained load, overload and backpressure, and failures or reconnections. Include warmup and repeated runs, and retain raw measurements so results can be checked.
- Report the boundaries. State exactly what each latency measurement starts and ends at, the test environment, and whether connection setup is amortized across persistent connections.
This produces a deployment-specific comparison rather than turning a result from one “remote SSE” setup into a claim about every HTTP-based MCP server.
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