The verdict in three sentences
Exposing your data to partners through a custom REST API costs in Berlin in 2026 between 15,000 and 50,000 EUR, depending on the number of endpoints and the security level. The real challenge isn't the first version but governance: authentication, rate limiting, versioning and documentation that avoid breaking everything at each change. A well-designed API becomes a commercial asset that opens new B2B revenue streams.
Pricing by API tier
The budget follows directly from functional scope and security requirements. A simple internal API is nothing like a monetized public API bound by SLAs.
| API tier | Endpoints | Price (EUR) | Timeline |
|---|---|---|---|
| Simple internal API | 5-10 | 15,000 - 22,000 | 4-6 wks |
| Partner API | 10-25 | 22,000 - 35,000 | 6-10 wks |
| Monetized public API | 25-50 | 35,000 - 50,000 | 10-16 wks |
| GraphQL (unified schema) | variable | 25,000 - 45,000 | 8-14 wks |
| SOAP-to-REST migration | depends | 20,000 - 40,000 | 8-12 wks |
On top, budget for OpenAPI/Swagger documentation (2,000-5,000 EUR), a developer portal (3,000-8,000 EUR) and load testing.
REST or GraphQL, and which gateway?
REST stays the standard for varied consumers and HTTP caching. GraphQL shines when clients need flexible queries and fewer calls. The gateway (Kong, AWS API Gateway, Apigee) handles authentication, quotas and observability.
| Criterion | REST | GraphQL |
|---|---|---|
| Learning curve | low | medium |
| HTTP caching | native | complex |
| Over/under-fetching | frequent | avoided |
| Gateway cost/month | 100 - 500 EUR | 200 - 800 EUR |
| Rate limiting | per endpoint | per query/complexity |
| Ideal for | varied partners | data-rich apps |
Non-negotiable 2026 security practices: OAuth 2.0 or rotating API keys, per-consumer rate limiting, access logging, and explicit versioning (/v1, /v2) so you never break a partner in production.
Mini case study
Thomas, CTO of a 45-person logistics SME in Berlin, wants to expose parcel-tracking data to three carrier partners. Today he sends manual CSV exports: ~8 hours/week and frequent format errors. He commissions an 18-endpoint partner REST API for 29,000 EUR, with a gateway at 350 EUR/month. Partners consume data in real time: he saves ~8 hours/week (~1,900 EUR/month of loaded time) and signs two new contracts eased by the integration. Direct payback: around 14 months, excluding added revenue.
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FAQ
What does a custom REST API cost in Berlin in 2026?
Between 15,000 and 50,000 EUR depending on the number of endpoints and security level. A simple internal API starts around 15,000 EUR; a monetized public API reaches 50,000 EUR.
Should I choose REST or GraphQL?
REST suits varied consumers and HTTP caching; GraphQL reduces call counts for data-rich apps. Gateway cost runs 100 to 800 EUR/month.
Is documentation included?
It must be: OpenAPI/Swagger documentation costs 2,000-5,000 EUR and drives partner adoption. Without it, the API stays unusable.
How do you evolve without breaking partners?
Through explicit versioning (/v1, /v2) and an announced deprecation policy. You keep an N-1 version live for several months before retiring it.
What security budget should I plan?
OAuth 2.0, rotating keys, rate limiting and logs represent 15-25% of the budget. It's non-negotiable for an externally exposed API.
Let's scope your project. Share your target endpoints, your consumers (internal, partner, public) and your budget, and we'll frame a secure, documented, versioned API. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
