The decision nobody explains well
When a customer asks your SaaS to read their biometric terminals, there are two ways to answer. Build: your team studies the vendor's protocol, writes the adapter, sets up the infrastructure and keeps everything alive. Buy: you consume a managed API like API Connect that has already solved that problem and exposes the devices as REST endpoints.
The conversation usually starts off wrong because the wrong things get compared: the price of development against the price of the subscription. The right comparison is the total cost of ownership of the first year against one line in your budget. Here's why.
What Build really implies
Building your own integration is not a two-week sprint. It's a permanent module of your product with these components:
- Protocol engineering: terminals don't speak HTTP. Implementing push/ADMS mode means handling sessions, binary data-transfer formats and variations per firmware family. Every new model is a new dialect.
- Public infrastructure: for devices to connect to your SaaS, you need a server with a stable public address, TLS, high availability and 24/7 monitoring. It's not the same infrastructure as your business API: it's device infrastructure.
- Event storage: every punch arrives on its own; you need spike-tolerant ingestion, deduplication (terminals re-send on reconnect) and efficient queries by date range.
- Permanent maintenance: firmware updates change behavior, vendors fix bugs, customers report odd models. The adapter is never "done": it's maintained for life.
- Security: authenticating devices that have no username and password, with everything that implies in risk and auditing.
The bill nobody remembers: build consumes your best backend talent for weeks of initial development — and then reserves a fraction of that team forever. Meanwhile, your product roadmap kept waiting.
What Buy really implies
With a managed API, the adapter work, the connection infrastructure and protocol maintenance are already done and maintain themselves. Your share of the work is the part that actually adds value to your SaaS:
- Authentication: a standard login against the API gives you a JWT token with expiration.
- Consumption: per-terminal reports with date range and pagination, and real-time events (via webhook or stream) for urgent logic.
- Management: user and credential registration by serial number via API.
curl -X POST https://TU-DOMINIO-API/auth/login \
-H "Content-Type: application/json" \
-d '{"username": "tu_usuario", "password": "tu_password"}'
# Token ready to call the API
{
"access_token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9...",
"token_type": "bearer",
"expires_in": 3600
}The honest comparison
| Criterion | Build (your own adapter) | Buy (API Connect) |
|---|---|---|
| Initial development | Weeks–months of specialized engineering | Days: login, events, reports |
| Time-to-market | Whenever development ends + hardware testing | Demo the same day (sandbox included) |
| Maintenance | Permanent: firmware, models, network bugs | Included in the platform |
| Supported models | Only the ones you adapt, one by one | Everything the platform supports, from day 1 |
| Infrastructure | Your own public server + HA + monitoring | Nothing extra: you consume endpoints |
| 2-year total cost | High and growing (team + infrastructure) | Low and predictable (subscription) |
| Scaling | Your operational problem | Add terminals, not servers |
When Build DOES make sense
To be fair: there are cases where building is the right call. They all share these traits:
- You have a very specific requirement that no API exposes (for example, direct control of an unsupported peripheral).
- You have a dedicated engineering team that can take on indefinite maintenance without sacrificing the roadmap.
- Your product roadmap includes your own hardware: the adapter would be a strategic asset, not a patch.
- Volume justifies the investment: thousands of terminals where every cent per terminal changes the economics.
If your case is "my SaaS needs to read my customers' ZKTeco terminals", none of those four applies. You're in Buy territory.
The decision rule in one sentence
Build what differentiates your product; buy everything else. Your SaaS doesn't compete on parsing the ADMS protocol — it competes on better payroll, better condo management, better security. Hardware integration is a means, not your product.
With API Connect: the cost of integration becomes a subscription proportional to the number of terminals — a variable cost that grows with the revenue it generates, not a fixed team you have to feed month after month.
Frequently asked questions
Isn't it cheaper to build it myself?
The initial development looks cheap; the real cost lies in permanent maintenance and infrastructure. The API turns that fixed cost into a predictable variable cost.
Am I locked into the vendor if I use an API?
Your code consumes REST + JSON with standard auth: the most portable abstraction. Changing vendors means changing URLs and credentials, not rewriting your architecture.
What if I need something the API doesn't expose?
Evaluate before committing to the feature: in API Connect's sandbox you validate full coverage (events, reports, users, credentials) before deciding.
Compare with data, not intuition
Create your account, try the sandbox and measure how long it takes to get your first event running. 14 days free, no card required.