Resilient MCP Server - Deployment Decision

Decision: Railway.app (Starter) → VPS (Long-term)

Rationale

Railway (immediate, 1-2 weeks):

  • ✅ Auto-deploy on git push (zero config)
  • ✅ Free tier: $5/mo (easy to test)
  • ✅ Zero infrastructure management
  • ✅ Integrated monitoring + logging
  • ❌ Vendor lock-in (but easy to migrate)

VPS (after validation, weeks 3+):

  • ✅ Full control, cheaper long-term
  • ✅ Can self-host if needed
  • ✅ No vendor dependency
  • ✅ Multiple services on one box
  • ❌ Manual deployment, patching

Action Plan

Phase 1: Railway Setup (Week 1)

  1. Create Dockerfile 
    FROM rust:1.75-alpine AS builder
WORKDIR /app
COPY . .
RUN cargo build --release --manifest-path resilient/Cargo.toml
   
FROM alpine:latest
RUN apk add --no-cache curl ca-certificates libz3
COPY --from=builder /app/resilient/target/release/rz /usr/local/bin/
EXPOSE 8080
CMD ["rz", "--mcp-server", "--http-port", "8080"]
  2. Deploy 
    railway login
railway link EricSpencer00/Resilient
railway variable set Z3_BINARY=/usr/bin/z3
railway up
  3. Monitor
    • Dashboard: railway.app/projects/resilient
    • Logs: real-time tail in UI
    • Health: curl https://resilient-mcp.railway.app/health

Phase 2: Validation (Week 2)

  • Claude Code integration test
  • 24-hour uptime verification
  • Cost confirmation
  • API performance baseline

Phase 3: VPS Migration (Weeks 3+)

  • Provision Hetzner/DigitalOcean box ($5-10/mo)
  • Deploy via systemd + auto-restart
  • Migrate DNS to VPS
  • Archive Railway

MCP Tools to Expose

Tier 1 (MVP - Week 1) 

{
  "tools": [
    {
      "name": "rz_compile",
      "description": "Compile Resilient code and return diagnostics",
      "input_schema": {
        "type": "object",
        "properties": {
          "code": { "type": "string" }
        }
      }
    },
    {
      "name": "rz_format",
      "description": "Format Resilient code",
      "input_schema": {
        "type": "object",
        "properties": {
          "code": { "type": "string" }
        }
      }
    }
  ]
}

Tier 2 (If time - Week 2) 

{
  "name": "rz_verify",
  "description": "Verify contracts with Z3",
  "input_schema": {
    "type": "object",
    "properties": {
      "code": { "type": "string" },
      "verify_contracts": { "type": "boolean", "default": true }
    }
  }
}

HTTP API Specification 

POST /mcp/call
Content-Type: application/json

{
  "tool": "rz_compile",
  "input": {
    "code": "const X = 5; println(X);"
  }
}

←

{
  "status": "ok",
  "stderr": "",
  "stdout": "",
  "diagnostics": []
}

Costs

Service Monthly Notes
Railway $5-20 Free tier includes 500 compute hours; easy to scale
Hetzner VPS $5.99 2 vCPU, 4GB RAM; plenty for single MCP server
Domain $12/yr resilient-mcp.dev or similar
Monitoring Free (built-in) Railway provides; use Healthchecks.io if self-hosted

Total: $15-40/month (very reasonable for production service)

Security

  • API rate limiting: 100 req/min per IP
  • Input validation: max 10MB code per request
  • Timeout: 10s per compile
  • No secrets in logs
  • TLS only (https)
  • CORS: Claude Code origins only

Success Metrics

  • Endpoint responds in <2s (p95)
  • 99.5% uptime SLA
  • Zero authentication errors from Claude
  • <$20/mo cost
  • Rollback-able in <5 min

Next Steps

  1. Today: Create Dockerfile + test locally
  2. Tomorrow: Push to Railway
  3. Week 1: Validate with Claude Code
  4. Week 2: Plan VPS migration