How to Enforce API Usage Policies

How to Enforce API Usage Policies

One of the most difficult aspects of creating an API service for public consumption is the balance between developer control and user freedom. Ensuring that users can leverage an API to new heights requires a certain amount of freedom, both in modality of usage and in applicability of the use case. The security of underlying systems and the API itself relies on controlling this usage and ensuring a level of control for the greater good. The balance between these two is complicated, depending on a variety of API usage policy enforcement mechanisms. These policies can be tricky to implement, however, and their enforcement can present difficulties both obvious and not. Let’s dive into some of those challenges when it comes to the limits of API usage.

Major Challenges for Effective Usage Policy Enforcement

External System Integration

The most immediate problem for most APIs in terms of enforcement is where the API usage actually occurs. It’s often easier to enforce use policies when the interaction is happening natively on the API, but APIs are designed for external use and implementation. When APIs are used as part of an external system, this dynamic can result in uses that are outside of the visibility of the enforcement scheme.

For instance, if your API is implementing a limit based on origination, that is relatively easy to enforce access control on a native application. What if someone is using your API in a way that funnels their own service’s calls into a single unified endpoint that then connects to your API? In such a case, origination is obfuscated, and this can be difficult to identify and mitigate with API governance.

Differentiation Between Security and Business Limits

While these topics are often considered one in the same, there is a very big difference between limiting based upon security reasons and limiting based upon business concerns. Rate limiting is often implemented for very clear security reasons, preventing Denial of Service attacks and alert fatigue. Business-centric quotas, however, limit API interactions based upon business needs.  While an external system might handle business quotas, rate limiting might be managed by an API gateway – the reality of this implementation means that you have the same effective process split into two very different categories and two very different systems, increasing complexity of design and reducing clarity in operation at the top level. This can be further complicated when you introduce business-to-business relationships that might bypass the business logic and depend on the rate limiting logic as a mode of “API protection” implementation for the business logic itself. This can obviously get very complicated very fast.

Inter-System Communication

The reality of the microservice paradigm and the business-to-business marketplace is that systems are almost never located in a single place. Monitoring might occur using one system while enforcement occurs with another. Rate limiting might be handled by different systems both internal and external depending on the origination of the request. Sometimes, microservices will have their own systems for monitoring that are separate from a centralized enforcement, and in some cases, the opposite may be true! Ultimately, the communication between these systems represents a major challenge, as usage policy enforcement is complicated with each additional system.

Customization and Flexibility

Business needs change, sometimes week to week and day to day. Due to this, business needs to be flexible. In order for a business to be flexible, best practices for the systems that are in place to support the business is to also be flexible. 

This can drastically increase the complexity of enforcement – usage policies that are static are relatively easier to uniformly enforce across different systems, as the end result is the same regardless of the use case or origination. When you introduce differentiation based on custom requirements or changing business environments, you may very quickly enter a situation where multiple disparate systems must be updated to varied and complex needs and goals. The API manager must ensure that the acceptable use policy is up to date and that any API policy or security policy centered on mitigating vulnerabilities are adaptable to their varied user base. 

Real-Time Monitoring and Enforcement

Effective enforcement requires effective monitoring, and this monitoring often has to be real-time to be proactive as opposed to reactive. This introduces additional layers of complexity, however, as real-time monitoring requires adequate system design and resource allocation. Discrepancies in monitoring of API traffic can lead to massive breaches in usage policies, exposing businesses to legal and economic problems should sensitive data be accessed.

Unfortunately, this requirement introduces cost and complexity to the equation. There is no way to solve this problem except through proper resourcing and security testing, both of which cost time, money, and attention. This adds application security challenges to any business, but is especially problematic for startups and other businesses trying to effectively manage capital and resourcing.

Transparency and Reporting

Business and technical operation requires transparency and reporting. Businesses need clear insights into their API state, API data, and the state of its use across varied user groups to ensure compliance with policies and alignment to goals. The lack of transparent reporting can make effective enforcement difficult, and the implementation of effective transparency and reporting systems again introduces cost in terms of capital and complexity.

Exceptions Without Compromise

Nothing is set in stone – as a fundamental business approach, exceptions to usage policies will occur. How these exceptions are managed is vital to decreasing API vulnerability . Do you have a promotional period? Do you have a special policy for non-profit clients? How do you handle coupons, sales, an incoming request, etc. that may include usage exceptions? Every new exception introduces complexity, but every new exception could carry with it significant business upside for an API provider, both in terms of monetary goals and utilization numbers.

API management and balancing these exceptions introduces more complexity into the equation, but also requires increased transparency and reporting to ensure the API security exceptions are just that – exceptions, and not the steady state or rule.


While usage policies are fundamental to effective management and monetization of APIs, enforcement presents several challenges. Thankfully, there’s a fully featured solution – Moesif. We have developed a core set of features designed to provide effective solutions to all the specific API issues noted above.

Moesif enables deep understanding of API responses and usage to understand the intent behind the user. By surfacing signals around adoption and usage, Moesif delivers unprecedented insight and authentication into the consumer behavior, unlocking new paths of iteration. Our powerful analytics tools provide additional deep insight into the customer behavior and utilization paradigm, allowing for effective establishment and measurement of usage across the board.

This enforcement is carried forward into a variety of channels, including behavioral emails and workflows to notify consumers who meet various usage criteria such as those approaching rate limits and those using deprecated APIs. A powerful enforcement system leverages quota and governance approaches designed to increase security, deliver more performant monetization, and improve consumer experience.

Moesif can be an effective solution to all of the issues noted here. Ready to join a product with powerful and proven tools? Schedule a demo today.

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