Single-tenant vs Multi-tenant: What I Wish I Knew When I Started

I should be coding right now, but instead, I went down the single-tenant vs multi-tenant rabbit hole. Then I got lost in videos, articles, and posts that all said different things.

One person says multi-tenant is the only way to scale. Another says single-tenant is the only way to be secure. And someone always warns: “If you choose wrong, your SaaS will fail.”

It’s really not that serious. I just wanted a simple explanation without all the technical words and drama. So here’s the version I wish I had read earlier.

---

TL;DR

• Multi-Tenant (Apartments): Cheaper, easier to update, and perfect when you’re starting.
• Single-Tenant (Houses): Private, secure, and flexible, but expensive and hard to maintain.
• Hybrid (Schema-per-Tenant): Each tenant has its own schema in the same database. It’s more complex but gives better separation.
• Security: Multi-tenant apps must have strong data separation. One missing WHERE clause can leak data.

If you’re building your first SaaS, multi-tenant is usually the better choice.

---

The Analogy (Houses vs. Apartments)

Single-Tenant = Everyone Has Their Own House

Each customer has a private house, their own driveway, kitchen, and mailbox. In SaaS, that means a separate app and database for each one.

Advantages:

• Very secure: If one house is broken into, others are safe.
• Easy to customize: You can change things for one client without affecting others.
• No noisy neighbors: No performance issues between users.

Disadvantages:

• Expensive: More infrastructure means higher costs (servers, databases, monitoring)
• Hard to update: You must update each app separately.
• More maintenance: fixing one problem often means fixing it many times.

When to use it:

• When you work with enterprise clients who specifically ask for it.
• If you’re in a highly regulated industry (healthcare, finance, etc.) that needs strong compliance (HIPAA, SOC 2, and so on).
• When your users want custom deployments or on-premise hosting.
• If you actually have funding or a big budget to handle the extra infrastructure.

Multi-Tenant = One Big Apartment Building

Everyone lives in the same building, but each apartment has a lock. In SaaS, it means one app and one database, but data is separated by tenant IDs.

Advantages:

• Much cheaper: Resources are shared.
• Easier to update: One update affects all tenants.
• Simple to add new tenants: New signups are just new rows in your database.

Disadvantages:

• Security must be perfect: one small mistake can expose another tenant’s data.
• The "noisy neighbor" problem:: A heavy user can slow down others.
• Harder to customize: Individual tenant customizations are more complex
• More complex queries: Every query needs tenant filtering logic

When to use it:

• You're bootstrapping or indie hacking
• You want to launch and iterate fast
• Your users have similar needs (same features, pricing tiers)
• You're using modern frameworks with built-in tenant isolation

Schema-per-Tenant = Separate Floors in the Same Building

One database server, but each tenant gets their own schema (namespace).

How it works:

• Each tenant has tables like tenant_123.users, tenant_123.orders
• Your app switches schemas based on who's logged in
• Better separation than row-level filtering, cheaper than separate databases

Advantages:

• Better isolation than pure multi-tenant
• Easier to backup/restore individual tenants
• Still cheaper than full single-tenant
• Can migrate specific tenants to their own database later

Disadvantages:

• More complex than simple multi-tenant
• Some ORMs don't handle this well
• Database connection pooling gets trickier
• Migration scripts need to run on all schemas

Popular tools:

• Django: django-tenants (formerly django-tenant-schemas)
• Node.js: Knex.js with schema switching, or Prisma with multi-schema support
• Ruby on Rails: Apartment gem

- Postgres: Built-in schema support

Security (The Scary Part)

Multi-tenant security means more than just adding a tenant_id column.

Three Levels of Protection:

1. Database: Use row-level security or tenant views.
2. Application: Always filter queries by tenant.
3. API: Make sure tokens connect users to the right tenant.

Common mistakes:

• Forgetting WHERE tenant_id = ? → Instant data leak
• Wrong JWT token → Can access another tenant's data
• Admin panels that bypass tenant filters → Privacy nightmare
• Sharing caches across tenants → Information disclosure

Tools That Help:

• Supabase: Built-in RLS, auth hooks, and tenant isolation patterns
• Prisma: Row-level security middleware and tenant filtering
• PostgREST: API that enforces Postgres RLS automatically
• Django Tenants: Mature library for schema-per-tenant in Django
• PlanetScale: Database branching makes tenant testing easier

Security Best Practices:

• Use Postgres RLS as your backup layer
• Choose an ORM that enforces tenant filtering by default
• Include tenant_id in all JWT tokens
• Create separate admin roles with explicit permissions
• Test with multiple tenants in every environment
• Log all cross-tenant access attempts
• Use database-level constraints where possible

---

Why I chose multi-tenant

1. I'm bootstrapping. Single-tenant would be too expensive
2. My users don't need custom setups.
3. I want to move fast. One update for all tenants
4. I can always switch later Big clients could get single-tenant setups.

---

What Should You Do?

Go multi-tenant if:

• You're bootstrapping or self-funded.
• You want to launch fast.
• Your users have similar needs.
• You don’t deal with heavy security rules.
• Infrastructure costs matter

Go Schema-per-Tenant If:

• You want better isolation than pure multi-tenant
• You plan to offer data export/backup per tenant
• You might need to migrate large clients later
• Your users have moderately different needs
• You're okay with more complex migrations

Go single-tenant if:

• You work with enterprise clients.
• You have funding for infrastructure.
• You need strict data separation.
• You offer custom setups.
• Clients demand it (and pay for it)

Final Thoughts

I spent too much time reading about this when I should have been coding.

Big SaaS companies like Notion, Vercel, Shopify, and Zoom also started simple and are still multi-tenant. Slack started multi-tenant, now hybrid.

The real problem isn’t “choosing wrong”, it’s never launching at all.

Many companies eventually use both: multi-tenant for most users and single-tenant for large clients like Stripe or GitHub.

If you’re still deciding, start simple. Build, launch, and learn. You can always improve later.

Comments

[Fyodor]

sass=>saas 😉

[Thea]

Lool that’s what happens when a frontend dev writes about SaaS instead of Sass 😂 Thanks for catching!