⚠️ BIG CALL OUT — READ FIRST
Multi-tenancy is foundational architecture, not a cosmetic feature.
It determines how all data, identity, and security boundaries behave in the platform. Getting it right early saves massive pain later.

That said, implementing full multi-tenancy for an IPaaS + MCP stack is a major software endeavor. It involves DB design, secrets management, observability, runtime isolation, and governance.

👉 This should be planned in the roadmap, not rushed into an MVP.
Early versions can run on simpler single-tenant or light-scoping patterns until scale or enterprise customers demand more.
The goal here is to make sure we know where this fits in the journey and can avoid costly rewrites.

Multi-Tenancy Guide for IPaaS + MCP

This is the architectural playbook for standing up a multi-tenant IPaaS that exposes MCP tools/agents to each tenant. It’s aimed at a larger design discussion—tradeoffs, boundaries, and how we keep tenants safe without blocking velocity.

1) Tenancy Model (Who owns what?)

Tenants: companies/workspaces that connect systems (Stripe, HubSpot, Google Drive, etc.) and run automations and MCP agents.

Scopes we must isolate:

• Config: connectors, flows, agent/tool catalogs, environment variables
• Runtime: jobs, queues, schedules, executions, logs
• Data: secrets, credentials, cached artifacts, transcripts
• UI/Admin: users, roles, audit trails, billing

Decision: Default to logical multi-tenancy (shared control plane & data plane) with the option for siloed tenants (separate DB/queues/VPC) for enterprise.

2) Identity & Access

• Tenant boundary: Required on every request (host, header, or org subdomain).
• Users & roles: Owner, Admin, Integrator, Analyst, Viewer, ServiceAccount.
• Principals for automations: Service accounts with scoped tokens; avoid user tokens for long-running jobs.
• MCP agent trust: Agents/tools run with the tenant’s identity; permissions map to connectors and data classes.

3) Secrets & Connectors

• Secrets store: KMS-backed vault; per-tenant encryption keys or per-tenant data-encryption-keys (DEKs) wrapped by a master key.
• Connector instances: connector_instance(id, tenantId, type, configRef, secretRefs, region)—immutable history of edits.
• Rotation: versioned secrets; roll forward without downtime; last-known-good tracked per instance.
• BYOK (Bring Your Own Keys): supported; we store references, not plaintext; decrypt only in connector runtime.

4) Configuration Layers (who can override?)

1. Platform defaults (safe timeouts, retries, token lifetimes)
2. Tenant policy (allowed connectors, data residency, PII redaction level)
3. Workspace/project (flow timeouts, concurrency)
4. Flow/run (one-off overrides, if permitted)

Rule of thumb: Lower levels may only narrow (not broaden) the upper-level policy unless a privileged role signs the change.

5) Data Isolation Options

• Shared DB + RLS: single cluster; Row-Level Security enforces tenant_id predicate in all tables.
• Schema per tenant: middle ground; helpful for export/restore.
• DB per tenant (silo): for large/regulated customers; paired with dedicated queues and optional VPC peering.

Artifacts to isolate: job payloads, MCP transcripts, tool outputs, temporary files, vector indexes, cached tokens.

6) Runtime & Execution

• Queues: partition by tenantId and optionally by priority.
• Concurrency: per-tenant limits + per-connector back-pressure (respect SaaS provider rate limits).
• Sandbox: job containers or workers with ephemeral filesystem and time/cpu/memory caps.
• MCP tools: run out-of-process; enforce capabilities manifest; deny unlisted operations by default.

7) Observability & Audit

• Logs/metrics/traces tagged with tenantId, connectorId, flowId, runId.
• Audit trail for: secret access, connector auth handshakes, policy changes, MCP tool use, data export.
• Retention tiers: configurable per tenant (e.g., 30/90/365 days).
• Tenant-visible traces: safe redactions, downloadable execution reports.

8) Safety & Governance

• Data classification: mark fields as PII, PHI, Financial, Public.
• Redaction at boundaries: strip/obfuscate sensitive fields in logs and LLM/MCP contexts based on classification + tenant policy.
• Egress controls: allowlist outbound domains per connector; deny arbitrary HTTP from agents.
• Human-in-the-loop (HITL): required approvals for destructive actions (delete records, send emails at scale).

9) MCP-Specific Considerations

• Tool registry per tenant: which tools are enabled; version pinning; deprecation policy.
• Context windows: limit what the agent can “see”—explicit grants to datasets or connector scopes.
• Determinism knobs: replayable prompts with input hashes; store minimal context necessary to reproduce.
• Prompt safety rails: inject system prompts that reflect tenant policies (PII handling, retention, citation rules).

10) Scheduling & Triggers

• Time-zone aware cron per tenant; daylight-saving safe.
• Event triggers: webhooks, file drops, CRM updates—tenant-scoped endpoints (unique secrets).
• Debounce & dedupe: idempotency keys per trigger to avoid storm repeats.
• Maintenance windows: tenant can pause schedules during blackout periods.

11) Performance & Cost Controls

• Rate limits: global + per-tenant + per-connector.
• Quotas: monthly run minutes, storage, data egress, MCP token budgets.
• Burst buckets: short-term spikes permitted within policy, then smooth.
• Cost visibility: tenant dashboards for usage; anomaly detection + alerts.

12) Regionality & Residency

• Data residency flag on tenant (US/EU/etc.).
• Connector routing honors residency (e.g., EU sheets ↔ EU workers ↔ EU storage).
• Cross-region copying requires explicit policy allow and audit trail.

13) Lifecycle: Onboarding → Offboarding

• Onboarding: invite users, bind domain(s), set policies, connect systems, create service accounts.
• Backup/export: tenant-scoped export (configs, flows, secrets references, not plaintext).
• Offboarding: disable schedules, revoke webhooks/OAuth, delete artifacts per retention policy, cryptographic erasure of DEKs.

14) Billing & Plans (even if simple at first)

• Plan sets limits (connectors, runs/month, storage, retention).
• Per-tenant overage rules (soft cap vs. hard stop).
• Enterprise toggles: siloed DB, dedicated queue, private networking, custom retention.

15) Change Management & Versioning

• Version flows & tools; support phased rollouts and rollbacks per tenant.
• Breaking changes require migration notes and tenant-level confirm gates.
• Config diffs and approvals for risky changes (e.g., widening data access).

16) Security Posture

• Principle of least privilege across everything.
• Zero trust between services; mTLS + short-lived service tokens.
• Secret access audited; decrypt only in memory, never log plaintext.
• Pen tests per release train; targeted tests for MCP tool escapes.

17) Enterprise “Silo” Checklist

When a tenant qualifies for isolation:

• Dedicated DB/schema and read replica for analytics
• Dedicated queues & worker pool with reserved capacity
• Optional VPC peering / private link to tenant systems
• Custom keys (per-tenant KMS CMK) and bespoke retention
• Contractual SLAs & incident runbooks specific to tenant

18) What “Good” Looks Like

• New tenant can self-serve to first automation in under 30 minutes.
• Every execution is traceable, replayable, and scoped to the right tenant.
• A noisy or failing tenant cannot degrade others (isolation works).
• Secrets are rotated, audited, and never leak in logs.
• MCP agents are useful but boxed in by explicit capabilities and policies.

Open Questions for the Room

• Which tenants need silo mode at launch vs. later?
• How strict do we make the default egress allowlist for MCP tools?
• What’s our minimum viable observability (logs/traces) that tenants can see without risking PII exposure?
• Do we start with row-level security or schema-per-tenant for the shared tier?

This guide is intentionally policy-first. When we’re aligned on the boundaries, we can layer in concrete implementations (DB choice, queue tech, MCP runtime, vault provider) with confidence.