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Apis Explained For Recruiters Rest Graphql Grpc

APIs Explained for Recruiters: REST, GraphQL, gRPC

When you're sourcing backend engineers or full-stack developers, understanding APIs is non-negotiable. You don't need to build APIs yourself, but you need enough technical fluency to evaluate candidates, understand their experience, and have credible conversations with hiring managers.

This guide cuts through the noise. We'll break down the three dominant API architectural patterns—REST, GraphQL, and gRPC—from a recruiter's perspective. By the end, you'll know what questions to ask, what experience to value, and how to position roles.

Why Recruiters Need to Understand APIs

Before diving into specific technologies, let's be clear about why this matters for your job:

Candidate Evaluation: When a developer claims they "built REST APIs," you need to understand the depth of that claim. Did they understand HTTP methods, status codes, and statelessness? Or did they just add /api/ to URLs? The difference matters.

Job Descriptions: Vague tech requirements lose good candidates. "API experience" tells you nothing. "Experience designing and scaling GraphQL APIs for mobile and web clients" attracts the right people.

Credibility: Technical hiring managers notice when recruiters don't understand their domain. One poorly worded question kills your credibility for the entire search.

Sourcing Efficiency: Understanding API architectures helps you identify candidate overlaps. Someone with strong GraphQL experience can often pick up gRPC concepts faster than someone with zero API background.

According to GitHub's 2024 State of the Octoverse report, REST API experience appears in 34% of backend job descriptions, GraphQL in 18%, and gRPC in 8%—but those percentages are climbing, especially in fintech, streaming platforms, and microservices companies.

What Is an API?

An API (Application Programming Interface) is a set of rules that allows different software systems to communicate. Think of it like a restaurant menu: you (the client) order from it, and the kitchen (the server) prepares what you requested.

In web development, APIs enable: - Mobile apps to fetch data from servers - Frontend applications to update databases - Different services within a company to talk to each other - Third-party integrations (Stripe, Slack, Twilio, etc.)

The three patterns we'll cover—REST, GraphQL, and gRPC—are different architectural approaches to building these communication channels. Each has tradeoffs, and the "best" API pattern depends on the problem you're solving.

REST APIs: The Industry Standard

What REST Is

REST (Representational State Transfer) is the most established API architecture. It uses standard HTTP methods and treats data as "resources" with unique URLs.

The core principles: - Resources: Everything is a resource (users, posts, comments) with a unique URL - HTTP Methods: GET (read), POST (create), PUT/PATCH (update), DELETE (remove) - Statelessness: Each request contains all info needed; the server doesn't store client context - Standard Status Codes: 200 (success), 201 (created), 400 (bad request), 404 (not found), 500 (server error)

REST in Practice

A simple REST endpoint structure looks like:

  • GET /api/users — retrieve all users
  • GET /api/users/123 — retrieve user with ID 123
  • POST /api/users — create a new user
  • PUT /api/users/123 — update user 123
  • DELETE /api/users/123 — delete user 123

Why REST Dominates

REST has been the industry standard for over 15 years. Here's why:

Advantage Why It Matters for Hiring
Simple to understand Easier candidate pool; less specialized knowledge required
HTTP-based Works with every programming language and framework
Cacheable Reduces server load; candidates need to understand performance optimization
Browser-testable Developers can test endpoints directly; indicates hands-on experience
Mature tooling Swagger/OpenAPI, Postman, hundreds of tutorials; candidates have resources

REST Challenges (The Real Conversation)

But REST has legitimate problems that led to GraphQL and gRPC:

Over-fetching: If you request a user, you might get all their data (address, preferences, payment history) even if you only need their name. This wastes bandwidth on mobile.

Under-fetching: To display a user's posts and comments, you might need three separate API calls (/users/123, /users/123/posts, /users/123/comments). N+1 queries kill performance.

Versioning headaches: API changes require versioning (/api/v1/users vs /api/v2/users). Managing multiple versions is expensive for engineering teams.

Inflexible response shapes: The server decides what fields clients get. If your mobile app only needs three fields but the endpoint returns 20, you've wasted bandwidth.

These aren't dealbreakers for many use cases—they're tradeoffs. But when hiring, understand whether candidates have only used REST or if they've confronted these problems and explored alternatives.

GraphQL: The Flexible Alternative

What GraphQL Is

GraphQL is a query language for APIs released by Facebook in 2015. Instead of hitting fixed endpoints, clients request exactly the data they need, nothing more, nothing less.

With GraphQL, your mobile app sends a query like:

query {
  user(id: 123) {
    name
    email
    posts {
      title
      createdAt
    }
  }
}

The server responds with exactly that structure—no extra fields, no additional requests needed.

Why GraphQL Exists

GraphQL solves the over-fetching and under-fetching problems that plague REST:

Problem REST GraphQL
Over-fetching Client gets all fields Client requests only needed fields
Under-fetching Multiple requests needed Single request with nested queries
Bandwidth (mobile) High Lower (mobile-optimized)
Version management Multiple versions needed Schema evolves without versioning
Response predictability Server-determined Client-determined

The GraphQL Experience

Developers love GraphQL's developer experience. Tools like Apollo Client and GraphQL IDEs let developers: - Self-document APIs through schema - Auto-complete queries (similar to IDE intellisense) - See deprecations and required fields upfront - Test queries directly in the browser

For hiring purposes, GraphQL experience matters most at companies building: - Mobile-first applications (Instagram, Twitter, Shopify) - Multi-client platforms (web + mobile + third-party integrations) - Microservices architectures - Real-time applications

GraphQL Challenges

GraphQL isn't a universal solution:

Learning curve: Developers new to GraphQL need time to understand schema design, resolvers, and data loaders. Expect 2-4 weeks of ramp time for a strong engineer.

Query complexity: Without controls, clients can write deeply nested queries that spawn hundreds of database queries. This requires query complexity analysis and rate limiting—not trivial.

Caching complexity: HTTP caching works differently with GraphQL (it's POST-based). Developers need to understand cache strategies, which is harder than REST's URL-based caching.

Operational overhead: GraphQL requires batching, query timeouts, and resolver optimization. These aren't plug-and-play; they require experienced engineers.

Over-engineering for simple APIs: If your API serves one client and never changes, GraphQL adds complexity without benefit. REST might be the better choice.

When evaluating GraphQL candidates, ask about their experience managing complexity. Have they implemented query depth limits? Data loaders? Rate limiting? These separate experienced GraphQL developers from those who've built simple toy projects.

gRPC: The Performance Champion

What gRPC Is

gRPC (Google Remote Procedure Call) is a modern RPC framework that treats APIs like function calls. Instead of HTTP's text-based request/response, gRPC uses Protocol Buffers (a binary format) for efficient serialization.

gRPC is purpose-built for: - High-performance microservices - Low-latency systems (financial trading, gaming) - Constant data streaming - Service-to-service communication

How gRPC Differs

Aspect REST GraphQL gRPC
Protocol HTTP/1.1, HTTP/2 HTTP/1.1, HTTP/2 HTTP/2 (required)
Message Format JSON (text) JSON (text) Protocol Buffers (binary)
Speed Slower Moderate Very fast
Payload Size Larger Moderate Smaller
Human-readable Yes Yes No
Streaming Limited No Built-in
Browser Support Native Native (Apollo) Requires proxy

Why gRPC for Performance

gRPC's advantages are measurable and specific:

Binary serialization: Protocol Buffers compress data into bytes, making payloads 3-10x smaller than JSON. For millions of requests daily, this saves bandwidth costs.

HTTP/2 multiplexing: Multiple requests use one connection. No more head-of-line blocking.

Streaming: gRPC supports server-to-client and client-to-server streaming natively. Perfect for real-time data feeds.

Type safety: Protocol Buffers require strict schema definition. Clients auto-generate type-safe code. Breaking changes are harder to introduce accidentally.

Real-World gRPC Use Cases

Companies using gRPC extensively:

  • Google: Internal infrastructure; YouTube backend
  • Netflix: Microservices communication
  • Square: Payment processing
  • Uber: Real-time location services
  • Discord: High-performance messaging

If you're recruiting for these companies or similar high-frequency trading, gaming, or real-time platforms, gRPC experience is valuable.

gRPC Challenges

Complexity: gRPC requires understanding Protocol Buffers, service definitions, and code generation. Steeper learning curve than REST.

Browser incompatibility: gRPC doesn't work in browsers natively. You need a proxy (grpc-web) or separate REST APIs for browser clients.

Debugging difficulty: Binary format isn't human-readable. Debugging requires special tools (grpcui, grpcurl).

Ecosystem maturity: Smaller ecosystem than REST. Fewer tutorials, fewer developers with hands-on experience.

Operational overhead: Service definitions, code generation, proto version management add operational complexity.

Choosing the Right API Pattern: A Recruiter's Framework

As a recruiter, you don't decide which API pattern a company uses—that's the CTO's decision. But understanding the decision framework helps you explain roles better and evaluate candidates more credibly.

When Companies Choose REST

  • Building simple CRUD applications (create, read, update, delete)
  • Public APIs where simplicity matters (payment processors, weather APIs)
  • Teams unfamiliar with microservices
  • Legacy systems; established REST codebases
  • When browser compatibility is critical

Recruiting note: REST roles are abundant. Candidates are plentiful. You can be selective about architecture maturity and performance optimization experience.

When Companies Choose GraphQL

  • Mobile-first products needing bandwidth efficiency
  • Companies with multiple client applications (web, mobile, third-party)
  • Rapid API evolution; frequent new requirements
  • Teams wanting better developer experience
  • Startups building modern greenfield applications

Recruiting note: GraphQL roles pay 8-15% higher than equivalent REST roles (based on Levels.fyi data) because fewer engineers have real-world experience. If you have GraphQL candidates, they're worth recruiting aggressively.

When Companies Choose gRPC

  • Microservices architectures with high performance demands
  • Real-time applications (trading platforms, gaming servers, livestream infrastructure)
  • Companies optimizing for bandwidth costs at scale
  • Services handling millions of requests per second

Recruiting note: gRPC roles are rare (maybe 3-5% of backend positions) but highly specialized. Candidates are scarce. Expect bidding wars for experienced gRPC engineers.

API Experience by Seniority Level

How to evaluate API knowledge by career stage:

Junior Developers (0-2 years)

Expected REST knowledge: - Implement basic CRUD endpoints - Understand HTTP methods and status codes - Use frameworks (Express, Django, Spring Boot) - Follow REST conventions consistently

Red flags: - Confuse POST and GET; use GET to modify data - Return 200 status for all responses (no 400, 404, 500 understanding) - Build endpoints without thinking about clients' needs

Mid-Level Developers (2-5 years)

Expected API knowledge: - Design REST APIs with versioning strategies - Implement or consume GraphQL APIs - Understand API performance and caching - Design schemas considering multiple client needs - Implement authentication/authorization (JWT, OAuth)

Plus signs: - Experience scaling APIs to millions of requests - Thought about over-fetching and under-fetching problems - Experimented with multiple patterns; made tradeoff decisions

Senior Developers (5+ years)

Expected API knowledge: - Architect APIs considering organizational scaling - Deep experience with 2+ API patterns - Mentored junior engineers in API design - Made business case decisions: REST vs. GraphQL vs. gRPC - Implemented complex patterns (rate limiting, query complexity analysis, circuit breakers)

Differentiators: - Production gRPC experience - GraphQL at scale (100+ resolvers, complex authorization) - API gateway experience (Kong, AWS API Gateway, Envoy) - Migration experience (REST → GraphQL, REST → gRPC)

Tools and Frameworks Recruiters Should Know

When reviewing résumés or discussing projects, know these commonly mentioned technologies:

REST Frameworks

  • Express.js (Node.js)
  • Django REST Framework (Python)
  • Spring Boot (Java)
  • FastAPI (Python)
  • Gin (Go)

GraphQL Implementations

  • Apollo Server (Node.js)
  • Hasura (auto-generates GraphQL from PostgreSQL)
  • GraphQL-core (Python)
  • Sangria (Scala)

gRPC Tools

  • Protocol Buffers (data serialization)
  • grpcurl (command-line gRPC testing)
  • grpcui (GUI for gRPC debugging)

API Tooling

  • Postman (REST/GraphQL testing)
  • Swagger/OpenAPI (REST API documentation)
  • API Gateway solutions: Kong, AWS API Gateway, Nginx

How to Source API Specialists

GitHub Signals

Using Zumo's GitHub analysis, look for developers with:

  • REST experience: Commits in repositories with "api," "server," or "backend" in the name
  • GraphQL experience: Repositories with "graphql," "apollo," or "hasura" dependencies
  • gRPC experience: Repositories with "proto" files or "grpc" dependencies; less common, higher signal value

Interview Questions to Ask

For REST specialists: - "Walk me through your most complex REST API. How did you handle versioning?" - "Tell me about a time you had to optimize API performance. What metrics did you focus on?"

For GraphQL candidates: - "Have you dealt with N+1 query problems in GraphQL? How did you solve them?" - "Describe your approach to schema design. How do you handle evolving requirements?"

For gRPC candidates: - "Why would you choose gRPC over REST for a particular project?" - "Tell me about experience with Protocol Buffers. How deep did you go into schema design?"

These questions separate candidates with project experience from those who've only read documentation.

Compensation Benchmarks (2025)

API expertise affects salary ranges:

Role REST Focus GraphQL gRPC
Mid-level $110-150K $125-170K $140-190K
Senior $150-210K $170-240K $190-280K

Ranges are for US markets, mid-large companies. Fintech/trading premium: +20-40%.

The premium for GraphQL and especially gRPC reflects: - Fewer available candidates - Specialized knowledge - Higher value in performance-critical systems - Steeper learning curves (candidates are self-selected for rigor)

FAQ

What API architecture should I expect most backend developers to know?

REST. 85% of backend engineers have production REST experience. GraphQL experience is increasingly common (35-40% of mid-level+) but still specialized. gRPC is rare outside performance-critical domains. When interviewing, assume REST fluency; test for GraphQL or gRPC specifically.

If a candidate knows one API pattern really well, can they learn another?

Yes. The underlying concepts—HTTP, serialization, request/response patterns, authentication—transfer. An experienced REST architect can learn GraphQL in 2-4 weeks of practical work. gRPC takes longer (4-8 weeks) because of Protocol Buffers complexity. Domain depth matters more than pattern breadth.

How do I write job descriptions for API-focused roles without being too technical?

Use the tradeoff language: "Design REST APIs serving 10M+ daily requests with complex caching requirements" or "Build GraphQL APIs supporting web, mobile, and third-party integrations." This attracts candidates solving that specific problem, not generic "API experience" seekers.

Is REST dead? Should I stop recruiting for REST roles?

No. REST is the default for non-performance-critical APIs and will remain dominant. Netflix, Stripe, GitHub, and Twitter all serve REST APIs to public/external clients. REST is the right choice for 60-70% of new APIs. Recruit REST specialists, but value architects who understand when to use GraphQL or gRPC instead.

How do I evaluate GraphQL and gRPC candidates if I don't have technical expertise in those areas?

Ask about specific problems they solved: "Tell me about the most complex GraphQL schema you designed. What challenges emerged?" Listen for depth: toy projects sound different than production systems at scale. Ask their hiring manager or conduct a technical pairing interview. Use Zumo to analyze their GitHub activity—code speaks louder than résumés.

Take Action: Build Your API Recruiting Vocabulary

Understanding APIs doesn't make you an engineer, but it makes you a credible technical recruiter. Start here:

  1. Learn by doing: Open Postman, make a GET request to a public REST API (try JSONPlaceholder or PokéAPI). See how status codes, headers, and responses work.

  2. Follow the conversation: When hiring managers discuss architecture, listen for "over-fetching," "schema evolution," and "microservices." You'll start recognizing patterns.

  3. Source deliberately: If hiring GraphQL engineers, look for candidates in Apollo, Hasura, and Relay communities. If recruiting for gRPC roles, check GitHub for Protocol Buffer expertise.

  4. Ask better questions: Replace "Do you know APIs?" with "Tell me about your most complex API design decision and the tradeoff you made."

The technical recruiters who move into leadership roles are those who understand their candidates' domains deeply enough to have real conversations. API architecture is foundational—master this, and you'll recruit backend engineers with credibility and speed.

Ready to source developers with verified API experience? Zumo analyzes GitHub activity to identify engineers by their real-world project experience, not just résumé claims. Filter by REST, GraphQL, or gRPC expertise based on actual contributions.