Match each MCP transport to its defining characteristic and correct deployment scenario

Attempt it

stdio

HTTP+SSE (deprecated)

Streamable HTTP

Quick reference

TL;DR

stdio is a local subprocess over stdin/stdout; HTTP+SSE was the deprecated two-channel remote transport; Streamable HTTP is the current single-endpoint remote standard.

Memory aid

Sign in for the mnemonic that makes this stick. See Pro pricing.

Easy to grasp

Think of three ways to talk to a helper. stdio is like passing handwritten notes to a coworker at your desk: instant, private, no phone needed. HTTP+SSE was an old long-distance setup with two separate phone lines, one to listen and one to speak, which kept dropping calls when the listen line broke. Streamable HTTP is the modern long-distance line: one number you call for everything, and it can keep streaming back to you when there is a lot to say. All three carry the same messages. They just differ in whether the helper sits beside you or lives across the network, and how reliably the line stays up.

Key concepts

MCP transports stdio transport Streamable HTTP transport JSON-RPC 2.0

Quick scan · 2–4 min

Everything important, quickly.

5 min: define transport versus protocol, then walk stdio (local subprocess), HTTP+SSE (deprecated two-channel), Streamable HTTP (single-endpoint current standard), and the local versus remote axis tying the match together.

Side-by-side

Transport	Channels	Network	Status / use
stdio	stdin/stdout, newline-delimited JSON	None, local subprocess	Current, local developer tools
HTTP+SSE	SSE server to client + POST client to server	Remote	Deprecated mid-2025
Streamable HTTP	Single endpoint, POST + optional chunked stream	Remote	Current standard for remote servers

Real-world examples

Real products, models, and research that use this idea.

Claude Desktop and Claude Code launch local filesystem and Git servers over stdio as child processes configured in a JSON config file.
Anthropic's 2025 MCP spec revision deprecated HTTP+SSE and made Streamable HTTP the recommended transport for remote servers.
Cloud-hosted MCP servers behind OAuth 2.1 expose a single Streamable HTTP endpoint so standard proxies and load balancers handle them cleanly.

Interviewer follow-ups

What an interviewer would ask next. Try answering before peeking at the approach.

QWhy did the asymmetric two-channel design of HTTP+SSE cause connection lifecycle problems?

Sign in or go Pro to see the approach for this follow-up.

QHow does Streamable HTTP decide between a plain JSON reply and a chunked stream for a given request?

Sign in or go Pro to see the approach for this follow-up.

QWhat security layer does remote MCP add that stdio never needs, and why?

Sign in or go Pro to see the approach for this follow-up.

60-second cheat sheet

The night-before-the-interview bullets. Scan these on the way to the call.

Sign in for 5 unlocks/day or go Pro for unlimited revision sheets. See Pro pricing.

References

Primary sources. Skim if you want the original framing.