Best practices for building a unified API

Best practices for creating unified APIs

Table of contents

Building a unified API for your product integrations can significantly accelerate development and reduce maintenance overhead. However, it's not always the right solution, and when it is, there are critical best practices to follow for success.

Before diving into implementation, it's essential to understand when unified APIs make sense. As we've covered in our complete guide to building unified APIs, unified APIs work best when you need to support the same core functionality across multiple APIs within a category, and when the APIs have similar data models and capabilities.

Start small and expand

The most successful unified API implementations begin with a focused scope and gradually expand. Here's how to approach this:

Start with one API: Choose the API that's most important to your business or the one with the clearest data model. This allows you to validate your approach, verify customer demand, and build a solid foundation.

Minimal interactions: Focus on one user story/job to be done. For example, fetching contact information or creating new records. Begin with basic read and write operations. Implement this end-to-end before adding additional functionality.

Minimal data model: Only include the fields you know are crucial for your customers. You can always add more fields later, but starting with too many fields can lead to unnecessary complexity and maintenance overhead.

Before expanding to additional APIs, make sure to validate the integration with your customers. Like any feature, integrations typically require several iterations to get right.

Unify on your own data model

Our number one learning from helping dozens of customers build unified APIs on Nango: Use your existing, internal data model (e.g. your Contact or Company data model) as the unified data model for your API. Reduce it to the relevant fields, but don't build on somebody else's model.

Why your data model works best: Your application's data model already contains all the fields you need for your product. You understand the nuances (e.g. fields required for certain features of your product), supported enums, and which fields are truly important versus nice-to-have.

Handle concept mapping: The hardest part of building a unified API is mapping concepts between your app and external systems. For example, your app might have "contacts" and "companies," while an external system has "leads," "users," "contacts," and "accounts." This requires tradeoffs and nuanced decisions that only you, as the creator of your product, can make effectively.

Consistency across your application: Using your own data model ensures consistency between your unified API and the rest of your application, reducing cognitive load for your development team and (hopefully!) reusable types and validations.

Unify the long tail, keep API-specific integrations for core systems

Not all integrations should be unified. Here's what we recommend, based on our experience:

Build API-specific integrations for the most popular APIs: If 40% or more of your customers use a specific system, consider building a dedicated, deep integration for that system outside of your unified API. This allows you to leverage API-specific features and provide a more polished experience.

Focus on limited interaction surfaces: Unified APIs work best when the interaction surface is limited. For example, fetching basic contact information (name, email, title) works well across many systems. The more nuanced the data requirements become, the smaller the chance of good support across all APIs.

Know when to stop: If you find yourself working against the unification (constantly adding exceptions, complex mapping logic, or missing critical features), it's time to reconsider. Unified APIs aren't the right answer for all integrations.

Design for extensibility

Your unified API will evolve. Plan for this from day one:

Nullable properties: Plan for nullable properties from the beginning. Unfortunately, not all APIs will support all fields in your model. Design your application logic to handle missing data gracefully.

Schema evolution: Consider how you'll migrate existing synced data when you change your schema. Strong typing helps tremendously when extending existing APIs.

Metadata APIs: For very dynamic cases, consider building a metadata API that lets you programmatically query which fields are supported by which APIs. This is especially helpful when showing forms to users for complex data entry that will be synced with the external API.

Centralize the unification logic

Keep all API-specific logic in one place to maintain a clean abstraction:

Single source of truth: Ensure you have one place for all API-specific logic. This could be an integration infrastructure like Nango, or your own internal interface.

Common interface: Establish a common interface and data model across all APIs. Each API should have one implementation per interaction type that implements this interface for the particular external API.

Clean separation: The goal is to have a clean abstraction that the rest of your application can use without knowing about API-specific details.

Expect nullable properties

Perfect unified APIs, where every property of every entity is supported by every API, are unrealistic in practice.

Embrace optional fields: Some properties or entities won't be supported by all external APIs. For example, most systems might offer a title property on contacts, but when an external API doesn't have this field, it might be better to leave it as null than to map some random field to it.

Establish required properties: If every property in your data model is nullable, the unified API loses much of its value because you'll need if-else statements for every property access. If possible, define a minimal set of required properties that all APIs must support.

Graceful degradation: Design your application to work well even when some data is missing. This might mean showing "Not available" for missing fields or using fallback values where appropriate.

Build a robust technical foundation

The technical infrastructure supporting your unified API is crucial for long-term success:

Invest in observability: Issues will happen, and there's nothing worse than an angry customer and a black box you can't debug. Implement comprehensive logging, monitoring, and alerting from day one. Monitor external API requests, operations (e.g. syncs, reads & writes), auth & access token refreshes, data validation errors, and incoming webhooks.

Handle common challenges: Rate limits, retries, pagination, change detection, and token refreshes are challenges you'll encounter repeatedly. Build a solid foundation to avoid re-implementing these for each interaction with every API.

Data validation: Use validation libraries like Zod (TypeScript), Pydantic (Python), or similar tools to enforce data quality. Enforcing validation rules close to the external API source helps catch errors early and reduces downstream bugs.

Recommended tooling

Here are the essential tools for building a successful unified API:

Validation library: Use Zod, Pydantic, or similar for data validation and type safety.

OAuth or API auth library: Handle authentication flows consistently across all APIs.

Background task runner: For handling sync operations, retries, and other asynchronous work.

Integration infrastructure: Consider using a platform like Nango (open source), which includes all of the above and has first-class support for unified APIs, including built-in authentication, data syncing, webhook handling, and observability.

Conclusion

Building a unified API is a significant undertaking, but following these best practices will set you up for success. Start small, use your own data model, know when not to unify, and invest in a robust technical foundation. Remember that unified APIs are a tool to accelerate development and reduce maintenance overhead, not a silver bullet for all integration challenges.

For more detailed guidance on implementation, check out our complete guide to building unified APIs and explore Nango's unified API capabilities for a robust foundation.

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