page:recipes:mcp server:express:response streaming

Host mcp server with Express: streamed responses

Summary

Deploy a mcp server built with Express on Ample using the streaming response service pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL, a managed PostgreSQL 16 database is auto-provisioned and injected as DATABASE_URL. Verified on Express: a Server-Sent Events endpoint read incrementally through the public HTTPS gateway: five one-second chunks arrived spread over time with the first within seconds (not buffered), a 70-second stream of 36 chunks completed past common 60-second idle timeouts, and a client that disconnected after two chunks was observed and recorded by the server (disconnected=true). Not separately tested: your event schema, reconnection strategy and any per-request duration ceiling beyond the 70 seconds measured; treat the mcp server-specific behavior as your application code.

Framework

• Framework: Express
• Workload: MCP server
• Release Status: published
• Support Status: verified
• Execution Status: ready

Prerequisites

• A Express project that builds and starts with the documented commands (npm install, npm run build --if-present, npm run start on the node-22 template)
• A PostgreSQL driver reading DATABASE_URL at runtime (auto-provisioned when omitted, or supplied with --env)
• An Ample account token with servers:write, databases:read

Infrastructure Requirements

1. Compute

   • Status: verified
   • Summary: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.

2. Postgres

   • Status: verified
   • Summary: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.

Limitations

• Verified on the node-22 template at s-1vcpu-1gb with the example fixture; other sizes, templates and Express major versions are not verified.
• The mcp server itself (your event schema, reconnection strategy and any per-request duration ceiling beyond the 70 seconds measured) is application code and was not separately tested; the pattern checks are what was verified.

Cost Estimate

• Monthly Amount: 10.0 USD
• Components:
  • app server: s-1vcpu-1gb - $5.0
  • managed PostgreSQL database: s-1vcpu-1gb - $5.0

Workflow Steps

• Build and start: npm install, npm run build --if-present, npm run start on the node-22 template. The server must bind 0.0.0.0 on PORT.
• Deploy: Run the synchronous deploy once and read the result (exit 0 live, 1 failed, 2 blocked). Re-running with no change is a no-op.
• Verify: Fetch the live URL and the pattern self-test route(s) (/p/streaming-response-service) from the example; then run your own checks. On failure read ample logs --kind build then --kind runtime.

Success Checks

• App responds on its public URL
  • Kind: http_get
  • Path: /
  • Expect: ample canary express patterns

Examples

• Express pattern fixture: Multi-pattern Express app whose streaming response service module was checked live; the module is under tests/deploy-canaries/_pattern-modules.