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API Development & Integration

The API development company that designs for the day the integration breaks

BinaryBrill is an API development company that builds the REST and GraphQL APIs your own apps, partners and customers consume, and handles third-party API integration services for the payment providers, carriers and SaaS platforms you don't control. This is custom API development carried out by our in-house senior engineers — not the deeper enterprise system integration work for the ERP, CRM or warehouse platforms you already run, which lives on our separate Enterprise Integrations page.

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A senior engineer replies within 24 hours — not a sales rep.

Why APIs and integrations break somewhere other than the demo

The API works — until a partner tries to integrate it

Resources are named inconsistently, one endpoint returns an error as a string and another as an object, and pagination was added later by whoever needed it first. Your own team knows the workarounds by heart. A partner does not, and every integration attempt turns into a support thread that should have been a read of the documentation.

The third-party API's documentation describes an older version

The sandbox behaves one way, production behaves another, and the field the docs say is required is actually optional — except when it isn't. Nobody discovers this until the integration is half-built, and the estimate that assumed the documentation was accurate is now wrong by weeks.

A sync fails quietly, and nobody notices until a customer does

A webhook is missed, a retry never happens, or a request is retried and creates a duplicate charge. Without idempotency keys and a dead-letter queue, a failed integration doesn't look like anything — it just looks like a record that never arrived, discovered days later during reconciliation.

Every new consumer means another bespoke conversation

There's no published schema, so each new partner, mobile client or internal team integrates by reading the source code or asking an engineer directly. What should be a documentation link becomes a scheduled call, and the API team becomes a bottleneck for work that shouldn't need them.

How an API development company designs for the API you own and the one you don't

Building an API and integrating one someone else built are different problems with different failure modes. The first is mostly a design discipline; the second is mostly a failure-handling discipline. We treat them as such rather than applying one playbook to both.

Resource and error design that holds up once someone else depends on it

Consistent resource modelling, one shape for every error response, and pagination and filtering that still work once a collection passes a few thousand records. These decisions are cheap to get right on day one and expensive to change once a partner has built against them.

Versioning and a published schema, planned before they're needed

An OpenAPI or GraphQL schema kept in sync with the code, and a versioning and deprecation policy agreed before the first breaking change is required. Partners integrate from documentation, not from reverse-engineering your source, and a new API version doesn't mean an emergency migration for everyone already live.

Third-party integrations tested against reality, not the documentation

We run the real API in a sandbox before writing production code, because vendor documentation and vendor behaviour diverge more often than any project plan accounts for. That's where the actual estimate comes from, not from the integration guide.

Failure treated as the normal case, not the exception

Retries with backoff, idempotency keys so a repeated request can't double-charge or double-create a record, dead-letter queues for what still fails, and a reconciliation view your operations team can act on rather than a log only an engineer can read.

What this covers

Pick the piece you need, or bring us the problem and we'll tell you which applies.

REST & GraphQL API Design

The foundation everything else sits on: resources modelled consistently, errors shaped the same way across the whole surface, and pagination and filtering that still perform once a collection is large. Getting this right early is what lets an API grow to twenty endpoints, and then two hundred, without a redesign.

Resource modelling that stays coherent as the API grows past its first few endpoints
One predictable error shape across the entire surface, not one convention per team
Pagination, filtering and sorting that hold up once a collection passes a few thousand records
Authentication and rate limiting (OAuth 2.0, API keys) designed in from the first endpoint

Custom API Development & Versioning

Custom API development scoped to your actual domain model rather than a generic CRUD wrapper, with a versioning and deprecation policy agreed before the first breaking change is needed. A published, current schema means partners can integrate unaided instead of asking an engineer what changed.

APIs built around your domain, not a boilerplate resource-per-table structure
Versioning and deprecation strategy agreed up front, including a communicated sunset timeline
Published OpenAPI or GraphQL schema kept in sync with the code, not written once and left stale
Example clients or a starter SDK where partners need a faster path to their first successful call

Third-Party API Integration Services

Connecting to systems you don't control — payment providers, carriers, identity providers, niche SaaS tools — is mostly a failure-handling problem wearing an integration's clothes. We test the real provider in a sandbox before writing production code, because that's where the actual constraints show up, not in the integration guide.

Sandbox testing against the real provider before a line of production code is written
Payment providers, carriers, identity providers and niche SaaS APIs integrated on their terms
Webhook handling with signature verification and replay protection
A documented list of where the vendor's own documentation is wrong, before it costs you an incident

Resilient Sync & Failure Handling

Integrations fail — a provider times out, rate-limits you, or returns success while doing nothing. What matters is whether that failure is visible and recoverable, or a silent gap someone finds a week later during reconciliation.

Retries with exponential backoff instead of a request that fails once and is never tried again
Idempotency keys so a retried request can't double-charge a card or double-create an order
Dead-letter queues that hold failed messages for inspection instead of dropping them
A reconciliation view your operations team can act on, not a log file only an engineer can read

APIs That Enable Enterprise System Integration

Sometimes the job is putting a documented API in front of your own application or an ageing internal system, so something else can consume it without touching its internals. This is API design and exposure work. Connecting that API to the named enterprise platforms you run — your ERP, CRM or warehouse system — including whatever legacy protocol they actually speak, is a different discipline covered on our Enterprise Integrations page.

A documented API placed in front of an internal or legacy application so new products can consume it safely
Contracts and authentication designed to be consumed by your own systems as well as outside partners
Event or webhook emission so downstream systems can react without polling
A clean handover point to enterprise system integration work, which we scope and deliver separately

The stack we build on

Chosen to fit the problem — not because it's what we used last time.

API design & specification

OpenAPI (Swagger)
GraphQL
JSON Schema
AsyncAPI
Postman
Stoplight

Languages & frameworks

Node.js
NestJS
Python (FastAPI)
Java (Spring Boot)
.NET
Go

Reliability & messaging

Apache Kafka
RabbitMQ
Redis
AWS SQS
Temporal

Gateways, auth & documentation

OAuth 2.0
Auth0
Okta
Kong
AWS API Gateway
Redoc / Swagger UI

How we'll work together

Every stage ends with something in your hands — not a status update.

01
Contract and integration discovery
We identify who will call this API — your own apps, partners, customers — or which third-party APIs you need to integrate, and for the latter, get into a sandbox early to see how the provider actually behaves. Resource model, versioning approach and error format are agreed before anything is built.
You get: A written domain model and versioning policy, or sandbox findings and a risk list for any third-party API involved, plus a scoped estimate built on tested behaviour rather than documentation.
02
Design and publish the schema
The OpenAPI or GraphQL schema is drafted, reviewed and published before the bulk of the build starts, with conventions for errors, pagination and filtering fixed once and reused everywhere. A mock server means consuming teams can start building in parallel instead of waiting for the real endpoints.
You get: A published API specification, example requests and responses, and a mock server your frontend, mobile or partner teams can integrate against immediately.
03
Build against sandboxes with fault injection
Two-week sprints with a deployed environment throughout. For third-party integrations, we test against sandboxes with deliberately injected timeouts, partial responses and rate limits, so we see what breaks before your customers do.
You get: A staging environment updated each sprint, automated contract tests, an integration test suite covering failure scenarios, and code in your repository from day one.
04
Ship with monitoring and a reconciliation view
Launch includes alerting on failed syncs and dead-letter queue depth, dashboards for request volume and latency, and a reconciliation report your operations team can check without involving an engineer.
You get: Production deployment, monitoring and alerting dashboards, reconciliation reports, and API documentation and runbooks handed over to your team.

Where we've applied this

E-commerce & retail

Payment gateway, carrier and inventory API integrations kept in sync so checkout and stock levels don't quietly disagree.

SaaS platforms

A public API and webhook layer partners and customers can build against from documentation alone, without a support ticket for every integration question.

Logistics

Carrier tracking APIs from several providers normalised into one consistent event stream instead of five different formats.

Fintech

Payment processor, KYC and open banking APIs integrated with idempotency and an audit trail a compliance review can follow end to end.

Healthcare

Partner and patient-app integrations built against a documented API, with access control and request logging that hold up under review.

Travel & marketplaces

Supplier, inventory and booking APIs from multiple providers integrated behind one consistent interface for your own product to consume.

Questions buyers ask us

Do we need a dedicated API, or can our app just expose its database?

If more than one consumer needs the data — a mobile app, a partner, a second internal team — a dedicated API is worth it almost immediately, because a shared database becomes a shared liability the moment two consumers need different things from the same table. If there is genuinely one consumer with no plan to add a second, a full API is over-engineering, and we'll say so rather than bill for it.

Is this the same as enterprise system integration for our ERP or CRM?

No — related, but different work. This page covers APIs your own apps, partners and customers consume, and third-party integrations where you're writing the client-side code against payment providers or other SaaS platforms. Connecting the named enterprise systems you already run — ERP, CRM, warehouse, billing, payroll — to each other, including the legacy protocols they actually speak, such as SOAP, IDocs, EDI, flat files and scheduled SFTP, is a different discipline with a different failure mode. That work lives on our Enterprise Integrations page.

Should we build a custom API or use an API management product off the shelf?

The API itself is usually worth building custom, because it needs to reflect your domain. The layer around it — rate limiting, key management, analytics — is often better bought. Gateways like Kong or AWS API Gateway handle that well, and we'd rather wire one in than have you maintain a bespoke version of the same thing. We'll tell you during design where buying beats building.

What drives the cost of an API or integration project, and how long does it take?

For a new API: the number of distinct resources, how many consumers it has to serve on day one, and whether a versioning policy needs to be retrofitted onto something already live. For a third-party integration: how well the provider's real behaviour matches its documentation, which you only know once you're in the sandbox. A single well-scoped integration is often a few weeks; a full API surface with documentation and versioning is typically closer to a couple of months, depending on how many consumers it has to satisfy at launch.

How do you handle customer data flowing through third-party integrations?

We keep the amount of data sent to any third party to what the integration actually needs, and encrypt it in transit as standard. Where a provider's terms allow customer data to be used beyond the transaction — for their own model training, for instance — we flag that during design so it's your decision, not an assumption we made for you. Credentials and API keys are kept in your own secrets manager, not hard-coded or held by us after handover.

When is building a custom API the wrong call?

When you have exactly one internal consumer with no realistic plan to add a second — a shared library or a direct database view is cheaper and there's nothing wrong with saying so. It's also the wrong starting point if what you actually need is several named enterprise systems kept in sync with each other; that's a system-integration problem with its own failure modes, and worth scoping as one rather than as an API project that quietly grows into one.

How do you deal with a third-party API whose documentation is wrong or incomplete?

We assume it will be, and budget for a sandbox investigation before committing to an estimate. That usually surfaces the undocumented rate limit, the field that's required in practice but marked optional, or the webhook that arrives out of order. Where the gap is serious enough to affect the timeline, we tell you before the estimate is finalised, not partway through the build.

What happens when a partner's integration breaks after we change the API?

It shouldn't, if versioning was planned properly — a new version ships alongside the old one, with a published deprecation timeline rather than a surprise cutover. Where a breaking change is unavoidable, we tell you which consumers are affected based on real usage data, not guesswork, so you can reach out before anything actually breaks.

Who writes the code, and where are they based?

Our own in-house engineers in Sahibzada Ajit Singh Nagar, Punjab — 45+ of them, with over a decade of combined delivery experience, delivering for clients in 15+ countries. Nothing is subcontracted. You meet the engineers who will be on your project before you sign, and the person demonstrating the work each sprint is the person who built it.

Tell us which APIs you need built or connected

Describe the API you're building, or the third-party service you need to integrate. A senior engineer replies within 24 hours with a straight read on the approach — including where a third-party's documentation is likely to be wrong before you find out the expensive way.

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