The verdict in three sentences
For a fintech in Singapore that wants to open its services to 30 integration partners, a complete public API costs EUR 14,000 to 37,000 (about USD 15,000 to 40,000) when built with our Casablanca delivery team. The budget depends mostly on security (OAuth2, quotas, logging), the quality of the developer portal and the presence of a sandbox. Plan 12 to 16 weeks and an availability target of 99.9%, meaning under 9 hours of downtime a year.
Components of a partner API and their price
A public API is more than exposed routes. Partners judge your platform on documentation clarity, integration speed and stability. Here is our 2026 grid, converted from dirham rates (indicative 10.8 MAD to 1 EUR).
| Component | Content | Indicative price |
|---|---|---|
| Design and OpenAPI 3.1 specification | Resources, versioning, error codes | EUR 1,850 to 4,150 |
| OAuth2 authentication | Client credentials, scopes, secret rotation | EUR 2,300 to 5,550 |
| API gateway and quotas | Rate limiting, per-partner keys, usage plans | EUR 1,850 to 4,650 |
| Business endpoints | Payments, accounts, signed webhooks | EUR 3,700 to 11,100 |
| Sandbox | Mock data, status simulation | EUR 1,400 to 3,700 |
| Developer portal | Interactive docs, sign-up, keys, changelog | EUR 1,850 to 5,100 |
| Monitoring and alerts | Latency, errors, public status page | EUR 900 to 2,800 |
A launch scope (specification, OAuth2, quotas, 10 to 15 endpoints, documentation) starts around EUR 14,000. A platform with a full sandbox, self-service portal and webhooks reaches EUR 28,000 to 37,000.
Security requirements to budget for
In fintech, security is not optional. The Monetary Authority of Singapore expects payment institutions to control third-party access (Technology Risk Management Guidelines), and the PDPA governs personal data shared with partners.
| Requirement | Implementation | Indicative cost |
|---|---|---|
| Encryption in transit | TLS 1.3, mTLS for sensitive partners | EUR 450 to 1,400 |
| Webhook signing | HMAC SHA-256, anti-replay timestamp | EUR 450 to 900 |
| Audit logging | Who called what, 12-month retention | EUR 900 to 2,300 |
| Penetration test | External audit before opening | EUR 2,800 to 6,500 |
| Secret management | Vault, rotation every 90 days | EUR 450 to 1,400 |
| PDPA compliance | Data minimization, documented processing | EUR 900 to 2,300 |
The penetration test is the most often forgotten item. It must be done before opening to partners, then every year.
12 to 16-week plan
| Weeks | Step |
|---|---|
| 1 to 3 | Workshops with 3 pilot partners, OpenAPI specification |
| 4 to 9 | Build OAuth2, gateway, endpoints |
| 10 to 12 | Sandbox, developer portal, documentation |
| 13 to 14 | Penetration test and fixes |
| 15 to 16 | Opening to 3 pilots, then to 30 partners |
Mini case study
Yusuf, CTO of a payments fintech in Singapore, currently integrates each partner by hand. Each integration ties up 2 developers for 3 weeks.
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
- Current cost: 30 partners x 6 developer-weeks x EUR 830 = EUR 149,400.
- With the public API and sandbox, partners integrate on their own, with about 4 days of support each: 30 x 4 x EUR 170 = EUR 20,400.
- Project: EUR 29,600, plus EUR 5,500 a year for maintenance and monitoring.
Savings exceed EUR 95,000 from the first wave of 30 partners, and integration time drops from 3 weeks to a few days.
FAQ
How much does a public partner API cost?
In 2026, budget EUR 14,000 to 37,000 with a nearshore team depending on security, sandbox and developer portal. Maintenance then runs 15 to 20% of the initial budget per year.
Why OAuth2 rather than a simple API key?
OAuth2 allows fine-grained per-partner rights (scopes), short-lived tokens and instant revocation. A single key exposes the whole scope if it leaks.
What is a sandbox for?
It lets partners test without touching real funds. On our projects, it cuts support tickets during integration by 60 to 70%.
How do we guarantee 99.9% availability?
With redundant hosting across two zones, checks every 60 seconds and a public status page. This level tolerates about 8 h 45 of downtime a year.
Should the API be versioned from day one?
Yes, a versioned URL (/v1) and a 6 to 12-month deprecation policy avoid breaking partner integrations.
Let's scope your project. Tell us which services to expose, your target number of partners and your regulatory constraints, and we will price your API with a costed budget and a 12 to 16-week plan. 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.
