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Why Query Endpoints Deserve More Love in API Design

· 5 min read
Mongezi Kasha
Mongezi Kasha
Full-stack Software Engineer

Ever opened an API spec and seen endpoints like /users, /users/{id}, and then suddenly /users/query and thought, "Wait… what's this one for?"

That's your query endpoint. It's one of those things that makes perfect sense once you understand the "why," but often flies under the radar when we talk about good API design. Yet, in the right context, query endpoints can transform how your clients fetch and interact with data.

Let's unpack what they are, when to use them, and why they deserve a bit more love.

What Are Query Endpoints?​

Think of a query endpoint as a smart search bar for your API.

Instead of creating multiple routes to handle different filters like /users/active, /users/over-30, or /users/from-cape-town you expose one flexible endpoint that can handle dynamic queries:

POST /users/query
{
  "age": ">25",
  "city": "Cape Town",
  "status": "Active"
}

The API then returns all users matching those filters. It's a simple concept, but it solves a big problem. It keeps your endpoint structure clean, scalable, and easy to evolve as business needs change.

Path vs Query Parameters​

You might be used to seeing endpoints like:

GET /users/{accountNumber}/age

or

GET /users?city=CapeTown

Here's how they differ:

Path parameters (like {accountNumber}) identify a specific resource — something that exists as one unique record in your system. Example: /users/12345/age means "get the age of that exact user."

Query parameters (like ?city=CapeTown) are optional filters that help refine results. You can include one, many, or none at all:

  • /users?city=CapeTown → fetch all users from Cape Town
  • /users?age=30 → fetch all users aged 30
  • /users → fetch all users, no filters

That optionality is powerful — it allows clients to customize requests without forcing them to provide every possible field.

Query endpoints take this idea a step further. Instead of passing optional filters in the URL, you send them in the body of a single POST /users/query request — allowing complex, structured filtering while keeping your URLs clean.

Optional Filters in Query Endpoints​

One of the best parts about query endpoints is that every filter can be optional. Clients can send only what they need, like:

POST /users/query
{
  "city": "Cape Town"
}

or even:

POST /users/query
{
  "age": ">25",
  "status": "Active"
}

Each request is valid — the API simply returns results based on whatever filters were included. That flexibility is what makes query endpoints so elegant.

When Should You Use Query Endpoints?​

Query endpoints shine when your application needs complex or dynamic filtering that can't easily be handled by traditional GET parameters.

✅ Use them when:

  • You have multiple optional filters that users can mix and match freely (like status, role, or createdDate).
  • You need advanced capabilities like sorting, pagination, or range-based queries.
  • You want to keep your API routes minimal and intuitive.

⚠️ Avoid them when:

  • You only need simple lookups (e.g., /users/{id}).
  • You can easily express filters using GET query parameters.
  • The endpoint's flexibility could pose a performance or security risk if filters aren't validated properly.

Real-World Example​

Before a recent design session at my current project, I'll admit I didn't know what a query endpoint was.

We were working on a feature for our transaction history module, where clients needed to fetch transactions based on date ranges, amounts, statuses, or combinations of all three.

At first, I assumed we'd create multiple endpoints: /transactionHistory/recent, /transactionHistory/completed, /transactionHistory/high-value, and so on.

But during the design session, the team proposed something new to me: a query endpoint.

That idea completely changed how I thought about API flexibility.

Here's what we ended up building:

POST /transactionHistory/query
{
  "status": "Completed",
  "minAmount": 500,
  "dateRange": ["2025-01-01", "2025-01-31"]
}

This single endpoint handled all our use cases filtering by date, amount, or status without needing separate routes. Even better, clients didn't have to provide every field. They could query just by status, or just by dateRange, depending on what they needed at the time.

That was my "aha" moment. I finally saw how query endpoints simplify API design while keeping it scalable for future requirements.

How to Design a Great Query Endpoint​

Here are a few best practices to keep in mind:

  • Keep it predictable. Use a consistent request and response structure across your API.
  • Support pagination and sorting out of the box. Your clients will thank you.
  • Validate inputs. Never trust that filters from clients are safe for direct SQL queries.
  • Document everything. Clearly list supported filters, data types, and expected behaviors.
  • Optimize performance. Use indexes or caching if you expect heavy querying.

For a deeper dive, check out Microsoft's REST API Design Guidelines.

Update: Thanks to Luthando Mntonga for pointing out the important distinction between path and query parameters, which inspired the additional section in this post.