One of the core tenets of SaaS is to be able to meter tenant usage and then bill your customers. However, there are a lot of challenges in handling that.

One of the core tenets of SaaS is to be secure. Security spans across many layers from controlling access with IP whitelisting or Private Link, validating access with authentication to validate identity, authorization to assign permissions to users within tenant organizations, auditing to record every activity, tenant isolation to guard against malicious tenants, regulatory requirements from securing third-party services accesses to operational processes to achieve different compliance standards, and so on.

To interact with the SaaS service, we will need to build some sort of UX (API, GUI, CLI) interaction. We will need UX for your core application and also for management operations like tenant onboarding, access control, account management, auditing, etc. For HubSpot, the core application is CRM, for MongoDB it's the database, for Zendesk it's customer service software.

SaaS applications need to be highly available, with several 9’s of SLA. We have to deal with all sorts of failures, ranging from hardware failures, software failures, hung processes, data center power outages, networking switch failures, degraded storage, to correlated failures, and so on. You will have to keep track of per-tenant SLAs not only to monitor their health and take proactive actions before their availability falls below their SLA, but also to take necessary actions to remediate common issues.

SaaS provisioning requires tenant account creation, user provisioning, figuring out the tenant placement, configuring the tenant, and storing all the metadata. We also need to set up all the infrastructure, deploy software, configure software based on user input, enable monitoring, set up certificates, secure end-to-end access, safely coordinate everything during failures, and notify users of the provisioning progress.

A SaaS application serves several tenants, and each tenant should be isolated from one another. Depending on where and how you want to deploy, you may choose one or more types of isolation for your application.

Building software distribution channel(s) is hard, costly and time-consuming. I have discussed the challenges in building and operating your Control Plane before. To learn more, please see older version here and newer version here

A typical startup journey looks like this:

• you have an idea,
• you validate the market,
• you design your app,
• you build your initial MVP,
• you raise some capital.

After raising the initial capital or in some cases just before, you are looking to monetize by finding a product-market fit. Now, you can spend the next few years to build an operating system for your software distribution (aka Control Plane) or or you can focus on your application to build core differentiation or competitive moat. Doing one of them is extremely hard, trying to do both will also add significant risk to the success of your business and long-term success.

Kubernetes (K8s) Operators serve as effective tools for automating certain aspects of the control plane. In fact, if you already possess an operator and are considering building your end-to-end SaaS solution, please refer to this page.

However, it's important to recognize that having a K8s operator represents a first step towards building SaaS:

We think that Terraform is an excellent IaC tool if you want to setup your cloud infrastructure once. However, when it comes to SaaS, we feel that it falls short on many grounds. Here are the basic set of things that are missing in Terraform to even accomplish proper infrastructure management for building SaaS.

Time and time again, we observe organizations grappling with the right design, consequently entangled in perpetual operations. Initially, with 5 or 10 customers, everything seems promising, but as you scale, the cracks start to appear from every direction.