Vetting Nearshore REST API Designers

Your API Is Your Product—Stop Treating It Like a Side Project

The REST API is the most important contract in modern software. It is the lingua franca of the digital world, the connective tissue that links your mobile apps, your web frontends, your partners, and your customers to your core business logic. It is not a technical implementation detail; it is the product, manifested as a machine-readable interface.

When the design of this critical asset is delegated to developers vetted only on their ability to write code in a specific framework, you are not just accumulating technical debt. You are systematically devaluing your entire technology platform and creating an anchor that will drag down your product velocity for years to come.

Good API design is an act of profound empathy—empathy for the future developer who has to maintain it, empathy for the third-party developer who has to integrate with it, and empathy for the product manager who needs to evolve it. It is a discipline that combines technical rigor with a deep understanding of the business domain. It is about creating an interface that is not just functional, but also discoverable, predictable, and a pleasure to use. This is a skill set that is exceptionally rare and almost completely invisible to traditional, algorithm-focused technical interviews.

Traditional Vetting and Vendor Limitations

The standard approach to vetting a developer for API experience is a superficial checklist. Does the résumé mention "REST," "JSON," and a web framework like Express, Django, or Spring Boot? Does the candidate know the difference between GET and POST? Can they write a simple CRUD endpoint? A typical nearshore vendor, optimized for speed and volume, will check these boxes and assign the developer to your API team. The result is an unmitigated disaster that unfolds in slow motion.

Six months later, your engineering organization is suffering from the classic symptoms of API design failure:

• The "Giant Ball of Mud" API: A single, monstrous /god-object endpoint that returns thousands of lines of nested JSON, including data that is irrelevant to 99% of its consumers. Your mobile team has to make this heavyweight call and then parse through the massive response just to display a user's name on the screen.
• Inconsistent Naming and Structure: The API uses camelCase for some fields and snake_case for others. Some endpoints expect user_id while others expect userId. Every new integration is an exercise in forensic archeology to figure out the correct conventions.
• Ambiguous Error Messages: When a request fails, the API returns a generic 500 Internal Server Error with a useless message like "An error occurred." Your frontend team has no idea whether they should retry the request, log the user out, or display a friendly error message.
• Painful, Breaking Changes: A developer needs to add a new field to a response. In doing so, they rename an existing field, breaking every single client that was depending on it. The mobile app crashes, the web app shows blank data, and a key partner integration goes down.

The business impact is a slow, grinding paralysis of product development. The promised agility of a services-oriented architecture has been replaced by the gridlock of a poorly designed and inconsistent set of API contracts.

How Axiom Cortex Evaluates REST API Design

Axiom Cortex moves beyond the superficial "What does REST stand for?" questions and focuses on the underlying design principles and trade-offs that are the hallmark of a true API architect. We use scenario-based exercises to test a candidate's ability to design a real-world API under realistic constraints. We evaluate them across four key dimensions.

Dimension 1: Resource Modeling and URI Design

This is the foundation of a clean RESTful API. It is the ability to look at a business domain and model it as a set of logical, hierarchical resources that can be manipulated through a clear and predictable URI structure.

We present a business problem, such as "Design an API for a project management tool," and evaluate how the candidate:

• Identifies Resources: Do they identify the core nouns of the domain, such as projects, users, tasks, and comments? Do they understand how these resources relate to each other?
• Designs the URI Structure: Do they create a logical and hierarchical URI structure that reflects the relationships between resources? For example, do they use /projects/{projectId}/tasks to represent the collection of tasks within a project? Do they use plural nouns for collections?
• Handles Complex Relationships: How do they model many-to-many relationships? For example, how would they represent the assignment of multiple users to a single task? Do they understand when to embed a resource versus when to link to it?

A low-scoring candidate designs URIs that look like remote procedure calls (e.g., /getTasksForProject?projectId=123). A high-scoring candidate designs a "graph" of resources that is intuitive for a developer to navigate and explore.

Dimension 2: HTTP Method and Status Code Discipline

The HTTP standard provides a rich and universally understood vocabulary for interacting with resources. A great API designer uses this vocabulary correctly and consistently to create APIs that are predictable and self-describing.

In our scenarios, we test whether a candidate:

• Uses HTTP Methods Correctly: Do they understand the semantic difference between POST, PUT, and PATCH? Do they know that GET and HEAD requests must be safe and idempotent?
• Employs Status Codes Accurately: Do they return meaningful status codes? Do they know the difference between a 401 Unauthorized (you are not authenticated) and a 403 Forbidden (you are authenticated, but you don't have permission)? Do they use 201 Created for a successful POST request and include a Location header? Do they use 202 Accepted for asynchronous operations?
• Designs Meaningful Error Payloads: When an error occurs (e.g., a 400 Bad Request due to a validation failure), do they design an error response body that provides clear, machine-readable information about what went wrong?

A low-scoring candidate treats all successful requests as a 200 OK and all errors as a 500 Internal Server Error. A high-scoring candidate uses the full range of HTTP status codes to provide precise and actionable feedback to the API client.

Dimension 3: Evolvability, Versioning, and Security

A successful API will live for a long time and will need to evolve to meet new business requirements. A great API designer anticipates this and builds for change.

We evaluate a candidate's ability to think about the long-term lifecycle of an API, asking them to:

• Design for Backward Compatibility: How do they add a new feature without breaking existing clients? They should be able to discuss strategies like adding new, optional fields to JSON payloads and avoiding the removal or renaming of existing fields.
• Articulate a Versioning Strategy: When a breaking change is unavoidable, how should the API be versioned? They must be able to discuss the pros and cons of different versioning strategies (e.g., in the URI path, as a query parameter, or in a custom request header) and justify their choice for a given scenario.
• Implement Pagination, Filtering, and Sorting: For collection resources, how do they design a scalable mechanism for clients to retrieve data in manageable chunks? They should be able to design clear and consistent query parameters for these features.
• Think About Security from Day One: How do they handle authentication and authorization? Do they understand the principles of OAuth 2.0? How do they protect against common API vulnerabilities like insecure direct object references (IDOR) and mass assignment?

Dimension 4: High-Stakes Communication and Documentation

An API is only as good as its documentation. An undocumented or poorly documented API is a liability. An elite API designer is also a clear technical writer and a skilled communicator.

Axiom Cortex simulates the real-world need for clear communication, evaluating how a candidate:

• Writes Clear and Concise Documentation: We ask them to write the documentation for an endpoint they have designed. We look for clear explanations of the resource, the expected request payload, the possible response payloads, and example requests and responses. Familiarity with standards like OpenAPI (Swagger) is a strong positive signal.
• Negotiates an API Contract: In a role-playing exercise, we have them negotiate an API design with another "engineer" who has a different set of requirements. We observe whether they can defend their design choices while also being pragmatic and willing to compromise.
• Explains a Design Decision to a Non-Technical Stakeholder: Can they explain a complex API design choice (e.g., "Why are we using eventual consistency for this feature?") to a product manager in terms of its impact on user experience and development speed?

From a Technical Liability to a Strategic Platform

When you staff your teams with engineers who have demonstrated deep competence in API design through the Axiom Cortex process, your API platform transforms from a source of friction into an engine of innovation.

A B2B SaaS client was struggling to scale their partnership program. Their core API was a brittle, poorly documented "internal" API that had been exposed to partners. Every new partner integration required weeks of hands-on support from their most senior backend engineers. Using the Nearshore IT Co-Pilot, we assembled a dedicated "API Platform" pod of two elite nearshore engineers who scored in the top 5% on the Axiom Cortex REST API design assessment.

This team's mandate was not to add features, but to build a stable and self-service platform for partners. In their first four months, they:

• Published a Public API v2: They designed a new, clean, and consistent public-facing API, acting as a facade over the legacy internal systems. They used the OpenAPI specification to create a "contract-first" design.
• Built an Interactive Developer Portal: Using the OpenAPI specification, they automatically generated a beautiful and interactive developer portal with comprehensive documentation, code samples in multiple languages, and a "try it now" feature.
• Established a Deprecation Policy: They created and communicated a clear policy for versioning and deprecating old versions of the API, giving existing partners a predictable path for migration.

The result was a dramatic acceleration of the company's business. The time to onboard a new partner dropped from six weeks to under one week. The support load on the core engineering team was reduced by over 90%. The company was able to launch a new partner marketplace, creating a powerful new revenue stream that would have been impossible with the old API.

What This Changes for CTOs and CIOs

Investing in the quality of your API design is one of the highest-leverage investments a technology leader can make. It creates a platform that allows your entire engineering organization—as well as your partners and customers—to build value faster and more safely.

Using Axiom Cortex to vet for this skill allows you to change the conversation with your executive peers. Instead of talking about the backend as a cost center, you can talk about it as a product platform. You can say:

"We are investing in a public-facing API platform that will become a new channel for innovation and revenue. We have staffed this initiative with a nearshore team that has been scientifically vetted for their ability to design world-class, developer-friendly APIs. This platform will enable us to build new products faster, accelerate our partnership ecosystem, and create a durable competitive advantage."

This is how you transform your technology from a collection of applications into a true business platform.