The verdict in three sentences
A custom API to expose your data to the rest of the information system costs between 10,000 and 35,000 EUR in 2026, depending on the number of endpoints and security level. What really costs is not the first endpoint but the governance: documentation, versioning, OAuth authentication, quota management, and scalability. Expect 5 to 12 weeks and budget annual maintenance of 15 to 25% of the initial cost.
Cost per endpoint and per layer
A well-designed API is thought out by resources (customers, orders, products) and cross-cutting layers (authentication, logging, documentation). The first endpoint carries the infrastructure cost; the following ones are cheaper per unit.
| Element | 2026 cost (EUR) | Detail |
|---|---|---|
| API architecture and infrastructure | 2,500 - 6,000 | Gateway, environments, CI/CD |
| First endpoint (with foundation) | 2,000 - 4,000 | Includes reusable pattern |
| Subsequent endpoints (each) | 600 - 1,500 | Standard CRUD on a resource |
| OAuth 2.0 / OIDC security | 2,000 - 5,000 | Tokens, scopes, refresh |
| OpenAPI documentation / portal | 1,500 - 4,000 | Swagger, examples, sandbox |
| Testing and acceptance | 2,000 - 5,000 | Automated tests, load |
REST or GraphQL, and governance
The REST-vs-GraphQL choice depends on the API's consumers. REST remains the standard for simple, cacheable B2B integrations; GraphQL shines when clients have variable data needs. Governance (versioning, quotas, monitoring) is essential as soon as several teams consume the API.
| Criterion | REST | GraphQL |
|---|---|---|
| Upfront cost | 10,000 - 25,000 EUR | 15,000 - 35,000 EUR |
| Client-side learning curve | Low | Medium |
| Caching | Native (HTTP) | More complex |
| Flexible queries | Limited | Excellent |
| Versioning | By URL | By schema |
| Ideal for | Stable B2B integrations | Clients with varied needs |
Mini case study
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Nadia, IT director of a 200-employee distributor in Lille, wants to expose her catalog and stock to reseller partners via an API. Scope: 6 REST endpoints, OAuth, documentation, sandbox portal. Chosen quote: infrastructure 5,000 EUR, foundation + 6 endpoints 9,000 EUR, OAuth 3,500 EUR, docs 3,000 EUR, testing 4,000 EUR, i.e. 24,500 EUR over 10 weeks. Before, each partner received a manually processed CSV file: 20 hours/week in the back office. The API removes 900 hours/year at 32 EUR = 28,800 EUR/year, and opens a scalable partner channel. Payback in under a year.
FAQ
How much is an additional endpoint? Once the foundation is in place, budget 600 to 1,500 EUR per standard CRUD endpoint. Endpoints with complex business logic rise to 2,000-4,000 EUR.
Do you need OAuth or just an API key? An API key is enough for low-risk internal integrations. As soon as third parties access sensitive data, OAuth 2.0 with scopes becomes essential (2,000-5,000 EUR).
What annual maintenance should you plan? As an order of magnitude, 15 to 25% of the initial cost per year, i.e. 2,000 to 8,000 EUR. It covers security fixes, monitoring, and schema changes.
REST or GraphQL for B2B? For stable, cacheable partner integrations, REST is simpler and cheaper. GraphQL is justified if consumers have highly variable data needs.
How do you handle scaling? An API gateway with quotas and rate limiting, caching, and horizontal scaling. Scope it from the start: it is far cheaper than re-architecting under traffic pressure.
Let's scope your project. Tell us the data to expose, the estimated number of endpoints, and your consumers (internal, partners, public), and we will price the API and its governance. 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.
