How to Build API Integrations That Hold Up in Production
Building on an API is easier than it’s ever been. Better tooling, better documentation, better SDKs. The developer experience has genuinely improved.
Maintaining integrations in production is a different story. Rate limits, token expiry, silent failures, breaking version changes — the happy path is easy. Everything else is where integrations fall apart. This guide covers what actually breaks, how to build against it, and why the teams shipping the most reliable integrations aren’t building them from scratch. For broader context on where integration strategy is headed, see also the ultimate guide to API integrations.
Not all APIs are equal
Which tier you’re working with sets your expectations for everything that follows.
Tier 1: developer-first. Stripe, Twilio, GitHub. Well-documented, stable, versioned properly. Integrations here are straightforward.
Tier 2: functional but rough. Most SaaS tools fall here. The API exists and mostly works, but documentation is patchy and breaking changes happen without much notice. Plan for surprises.
Tier 3: legacy or portal-only. No public API, or one so limited it’s effectively useless. ERPs, government portals, insurance carriers, older CRMs. This is where most enterprise software lives, and where traditional API integration strategy runs out of answers.
Understanding which tier you’re dealing with upfront changes how you architect the integration, how much error handling you build in, and how much ongoing maintenance you should budget for. For Tier 3, the question isn’t how to build a better integration. It’s how to connect to a system that was never designed to be connected to. See how to connect software without APIs and our earlier piece on native integration vs. API for how teams handle that gap.
Where integrations break in production
Most integration failures aren’t caused by bad APIs. They’re caused by integrations that weren’t built to handle what production actually throws at them.
Rate limiting. Works fine in testing, falls over under real load. Build retry logic and exponential backoff from day one, not after your first 429 error.
Auth token expiry. OAuth tokens expire. API keys get rotated. Service accounts lose permissions. Any of these breaks your integration silently if you haven’t built re-auth handling in from the start.
Version deprecation. APIs change. The vendors that handle it well give you 12 months notice. Most don’t. Without active version management, a deprecation you missed becomes an outage today.
Silent failures. No error thrown, no alert fired, just wrong data flowing downstream. Comprehensive logging and response validation at every step is the only reliable defense.
Schema changes. A field gets renamed. A data type changes. These don’t always trigger errors but they break assumptions your integration was built on. Defensive parsing and regular integration tests catch these before they become incidents.
Teams that build integrations in-house absorb all of this themselves. Every failure mode, every maintenance cycle, every 2am outage. It compounds fast.
The three biggest challenges teams don’t plan for
Authentication complexity. Getting past the front door is harder than it looks. MFA, CAPTCHAs, session tokens, anti-bot detection — each requires specific handling. Teams building one-off integrations consistently underestimate how much time authentication alone consumes. Deck handles this across more than 100,000 portals, so you don’t have to engineer around each system’s auth quirks manually. For a technical deep dive, see inside Deck’s authentication system.
Maintenance never ends. Building the integration is only the first cost. Monitoring, debugging, keeping up with API changes, handling deprecations — this is where teams get surprised. A realistic integration roadmap accounts for maintenance as a recurring engineering expense. Deck’s agents are self-healing, adapting automatically when UIs change so your team isn’t burning cycles fixing broken connections. That tradeoff is covered in detail in our build vs. buy guide.
The missing API problem. The biggest challenge of all: many critical systems don’t have an API. Utilities, government portals, legacy enterprise software, insurance carriers — the data your product needs often lives behind a login screen with no developer access at all. Traditional integration strategy has no answer for this. Deck does. See how to connect software without APIs for the full picture.
How to build integrations that hold up
Whether you’re building in-house or on top of a platform like Deck, the fundamentals are the same.
Start with error handling, not the happy path. Every integration works when everything goes right. What separates reliable from fragile is how it behaves when things go wrong: retries, fallbacks, graceful degradation, clear alerting.
Build for re-auth from day one. Token expiry isn’t an edge case, it’s a certainty. Design for it upfront.
Monitor everything. Log every request and response. Set up alerts that fire before users notice something is wrong. You can’t fix what you can’t see.
Validate responses, not just errors. An API can return a 200 and still give you bad data. Check response shapes and values, not just HTTP status codes.
Document your own integration. How it works, what it depends on, what the known failure modes are. This documentation doesn’t exist anywhere else.
Deck gives teams a head start on all of this. Authentication, session management, resilience, and monitoring are built into the platform — not engineering problems you have to solve from scratch on every integration. Wire it in through the Deck API and avoid rebuilding the same plumbing on every connector.
When there’s no API at all
For Tier 3 systems, none of the standard advice applies because there’s nothing to integrate against. The answer is agent-based access: AI agents that interact with the system’s web interface directly, navigating pages, filling forms, extracting data, and submitting actions the way a human would. No API required, no vendor cooperation needed.
This is the core of what Deck is built for. Instead of maintaining brittle scrapers or waiting for a vendor API that may never ship, developers get stable, programmatic read and write access to any web-based system. Deck connects to more than 100,000 portals and handles everything that makes web automation hard: authentication, anti-bot defenses, session management, and self-healing when UIs change. Read how to automate legacy systems with computer use agents for a practical walkthrough.
Companies like Bilt, Ramp, Deel, and Wealthsimple use Deck to ship integrations that wouldn’t be possible any other way. Features that depend on complex backend access to systems with no API, delivered without the engineering overhead of building and maintaining it in-house.
The definition of API integration has expanded. It’s no longer limited to systems that expose official endpoints. Any web-based system is now a connectable system.
The bottom line
Most integrations don’t fail because the API is bad. They fail because they weren’t built to handle what production actually looks like. Getting the fundamentals right — error handling, re-auth, monitoring, validation — is what separates integrations that hold up from ones that page you at 2am.
And for the systems with no API at all, browser automation isn’t a workaround anymore. It’s the infrastructure. Deck is how teams ship it without building it from scratch. Start with how to connect software without APIs, or browse what Deck connects to to see coverage across portals and enterprise systems. Teams already on a unified API platform should also read our Merge.dev alternatives guide for how Deck fits alongside API-first integration stacks.