Custom code integrations for the work that does not fit Zapier, Make.com, or n8n. Direct API connections, custom auth flows, webhook architectures, ETL pipelines, and embedded integrations, production-grade reliability, fully owned by you.
This is API integration services in the original sense of the term: real engineering work that lives in your repository and runs on your infrastructure, not configuration inside a third-party automation platform. We pick this service when no-code tools cannot do the job, when the integration is part of your product, or when reliability and scale demand it.
DEFINITION
API integration services connect separate software systems through their APIs so data and tasks move between them automatically. This includes custom API development, third-party API integration, legacy system modernization, and testing and lifecycle automation.
Some API integration services are delivered through no-code or iPaaS platforms like Zapier, Make, or Workato. Others are delivered as owned code that lives in your repository and runs on your own infrastructure. Arius Automation works in both models across our services, but this page covers the custom-code side, the work no-code platforms cannot handle.
Production integrations shipped
Node.js, Python, TypeScript, Go
AWS, GCP, on-prem
A real integration in 13 lines of code. We write the rest. Auth, retries, validation, monitoring, deployment.
WHEN TO PICK THIS
No-code automation platforms are excellent at what they were designed for: standard integrations between common SaaS tools, run at moderate volume, with simple data transformations and standard auth. When the work moves outside those boundaries, the platforms either cannot do it or do it poorly. Common signs include:
The four scenarios below are where we usually get called in.
01
When the integration is a feature your customers see, it cannot live in a third-party automation tool. Customer-facing reliability, latency, and brand control all require the integration to run in your own infrastructure as part of your own product code.
02
OAuth 2.0 with refresh token rotation, mTLS, signed webhooks, enterprise SSO, custom JWT handling. The moment the auth model requires real implementation work, no-code platforms either lack support or implement it in ways that fail in edge cases.
03
At very high volume, no-code platforms either become expensive or hit rate limits. At very low latency, the abstractions in no-code platforms add overhead you cannot afford. Custom code lets you tune for the actual constraints.
04
Iterating over nested arrays, joining responses from multiple APIs, computing derived fields with business logic, validating against a complex schema, denormalizing for a downstream system. At some point, the work becomes engineering work, not configuration work.
INTEGRATION PATTERNS
Most integration work falls into one of six architectural patterns. Picking the right pattern is half the build. The other half is implementing it without skipping the parts that make production reliable.
Client → API Server → Database
PATTERN
The default for most modern SaaS integrations. We build clients that handle authentication, pagination, rate limits, retries, and schema validation. Often the foundation that other patterns sit on top of.
Source → Webhook → Queue → Worker
PATTERN
Accept high-volume webhook events into a queue, process them in workers, handle retries on failure. The right architecture when you cannot guarantee the downstream system will be available when the event fires.
Client → GraphQL Gateway → APIs
PATTERN
A single GraphQL endpoint that aggregates data from multiple backend APIs. Reduces round trips for client applications, lets you evolve the API contract without coordinating with every consumer.
Source DB → ETL Pipeline → Target DB
PATTERN
Extract from one system, transform with business logic, load into another. Scheduled or event-driven. For data warehouse loads, reporting feeds, or system-to-system migrations that need to run repeatedly.
Event Source → Event Bus → Subscribers
PATTERN
Publish events to a bus (Kafka, SNS, EventBridge, Pub/Sub). Multiple downstream services subscribe and react independently. The right pattern when one upstream change needs to trigger many downstream actions reliably.
Your App → Integration Layer → Customer SaaS
PATTERN
Integrations your customers configure inside your product to connect their tools. White-labeled, multi-tenant, with secure credential storage and per-customer error isolation. Common in vertical SaaS and platform companies.
SYSTEMS
Salesforce and custom CRM systems, including embedded customer-facing integrations.
Need CRM structure instead of integration code? CRM & RevOps Consulting
Shopify, Amazon SP-API, and multi-channel order pipelines.
Payment processors and webhook-driven reconciliation with idempotency and replay protection built in.
HL7, FHIR, and HIPAA-regulated clinical systems.
On-premises systems and internally-built platforms with no modern API, wrapped in a modern interface.
Need an operational interface around the integration? Internal Tools & Dashboards
AUTHENTICATION
Most integration failures happen in the authentication layer. Tokens expire. Refresh flows break. API keys leak. The five auth methods below cover almost everything we work with. We implement each one with the failure modes baked in.
| Method | Typical use | What we handle | Complexity |
|---|---|---|---|
| API key | Simple server-to-server integration. Most SaaS APIs default to this. | Secret storage in env vars or vault, rotation, scoped keys per environment | LOW |
| OAuth 2.0 | User-authorized integrations. Connecting on behalf of an end user. | Full authorization flow, refresh token rotation, scope management, expiry handling, error recovery | HIGH |
| JWT / signed tokens | Service-to-service with short-lived credentials. Common in microservice and enterprise architectures. | Token generation, signature verification, key rotation, claim validation, clock skew tolerance | MEDIUM |
| HMAC signed requests | High-security webhook verification or partner integrations where request integrity matters. | Signature generation and verification, timestamp validation, replay protection, key versioning | MEDIUM |
| mTLS / certificate-based | Regulated industries, B2B partner integrations, enterprise SaaS with strict security requirements. | Certificate provisioning, mutual verification, cert rotation, CA management, fallback handling | VERY HIGH |
We have also implemented enterprise SSO (SAML, OIDC), custom auth schemes from legacy systems, and the long tail of one-off auth requirements that show up in real integration work.
REAL PROJECTS
Anonymized for client confidentiality. The architecture and decisions are real. The metrics are approximations where exact numbers would identify the client.
B2B SAAS
Our client's customers wanted to sync their CRM data into our client's product without IT lift. We built an embedded Salesforce integration where customers connect their own org via OAuth, choose which objects to sync, and the data flows in real-time through webhooks plus a fallback sync.
WHY CUSTOM CODE
Customer-facing reliability and multi-tenant credential storage made no-code platforms unsuitable. The integration is a product feature, not a backend automation.
FINTECH
A payment processor sending 50,000+ webhook events per day to our client. The existing webhook handler was missing events under load and double-processing on retries. We rebuilt it with proper queue topology, idempotency keys, and replay protection.
WHY CUSTOM CODE
At this volume, no-code platforms either rate-limit or silently drop events. The reliability requirements demanded a real engineering solution with monitoring and dead-letter queues.
HEALTHCARE
A healthcare client needed to bridge an older HL7-based clinical system with a modern FHIR-compatible application. Required full HIPAA compliance, audit logging of every message, and no third-party data processing.
WHY CUSTOM CODE
HIPAA compliance, custom message format translation, and on-prem deployment requirements ruled out every no-code option. This was bespoke middleware work.
E-COMMERCE
An e-commerce brand selling on five channels needed a single internal source of truth for orders. Each channel had different webhook payloads, refund flows, and inventory deduction logic. We built the aggregation layer that normalized everything into a single canonical order model.
WHY CUSTOM CODE
Five distinct schemas, complex deduplication logic, and downstream fulfillment routing made this far beyond what no-code platforms can model cleanly.
B2B SAAS PLATFORM
A SaaS platform wanted to offer customers an integration marketplace where third-party developers could build apps that connect to customer accounts. We built the OAuth provider side of the equation: app registration, consent flows, scoped tokens, revocation, audit logs.
WHY CUSTOM CODE
Being the OAuth provider (not consumer) is engineering work that no-code platforms do not even attempt. This required deep understanding of the OAuth 2.0 spec and PKCE flows.
THE STACK
No religion about languages or frameworks. We pick what fits the use case, the team that will inherit the code, and the infrastructure already in place. Below is the spread of what we work with most.
LANGUAGES
FRAMEWORKS
INFRASTRUCTURE
DATA AND QUEUES
OBSERVABILITY AND OPS
PRODUCTION RELIABILITY
The difference between an integration that works in a demo and one that survives in production is the six things below. Skip any of them and the integration becomes someone's problem at 2am within a year. We build them in from day one.
Every operation that creates or modifies data should be safe to retry. Network failures happen. Workers crash. Requests time out. Without idempotency, a retry causes duplicate orders, duplicate charges, duplicate emails. We build it in by default.
Transient failures are the rule, not the exception. Network blips, vendor API hiccups, rate limit windows. Retries should be smart: exponential backoff, jitter to avoid thundering herd, max retry caps to avoid infinite loops, dead-letter queues for what cannot be saved.
Every third-party API has rate limits. The polite integration respects them. The smart integration uses them as a signal for self-pacing. Our integrations track remaining quota, slow down before hitting the wall, and queue requests instead of hammering the API.
If you cannot see it, you cannot fix it. Every integration ships with metrics on throughput, error rate, latency, and queue depth. Alerts fire on anomalies. The first time you know something is wrong is not a customer complaint.
API keys, OAuth tokens, signing secrets, certificates. Storing them in env vars or config files is how integrations end up in breach reports. We use proper secret stores with rotation, audit logging, and per-environment isolation.
When a downstream system is down, your integration should not bring down your application. We design for partial failure: feature flags, circuit breakers, fallback paths, cached responses where appropriate. The integration fails softly while the rest of the system keeps running.
HOW WE BUILD
Integration work that ends up in production needs to be reviewed like production engineering work, not like configuration work. Below is how we build it, including the checkpoints where your team signs off before we move forward.
Map the systems involved, understand the data flows, identify the auth requirements, sketch the architecture options. We document constraints (volume, latency, compliance) before designing anything.
Detailed design: API contracts, data schemas, error handling strategy, deployment topology, monitoring approach. Documented as written specs your team can review like a real design doc.
Implementation against the design. Test-driven where it makes sense. Includes unit tests, integration tests, and load tests proportional to the production volume the integration will see.
Deploy to your staging environment first. Run end-to-end tests with real (test mode) credentials. Cut over to production with monitoring in place from the first minute. Rollback plan documented.
Full documentation: architecture diagrams, runbooks, incident response procedures, on-call playbook. Optional retainer if you want us to stay on for ongoing operations and improvements.
WRONG PAGE?
FAQ
What engineering leaders ask before signing. Click to expand any answer.
Different work, different audience, different deliverables. Zapier and Make.com are configuration of a no-code platform. This is custom code that lives in your repository, runs on your infrastructure, and integrates at the API level. We pick this service when no-code platforms cannot do the job, when the integration is part of a product feature, or when reliability and scale demand real engineering work.
READY TO TALK SHOP
Forty-five minutes. Walk us through the systems involved, the constraints (volume, latency, security, compliance), and what your team has already tried. We will tell you what an integration looks like, what stack we would pick, and what production-grade actually means for your case.
No pressure. Just value.
