An API to build for an app
The mobile or web app needs a back end: accounts, data, payments, notifications and integrations.
Technology
NestJS and Node.js development:
APIs that hold up
in production.
NestJS and Node.js APIs and back ends for mobile and web apps: business modules, PostgreSQL, authentication, real time and testing. NestJS or Node.js appears in seven of our eight case studies.
orders.module.ts1// orders.module.ts — illustration2@Module({3imports: [PrismaModule, PaymentsModule],4controllers: [OrdersController],5providers: [OrdersService],6exports: [OrdersService],7})8export class OrdersModule {}
● TESTS · CI · OPENAPINESTJS · POSTGRESQL · PRISMA
Situations
What brings a back-end project to us.
A Node.js back end that no longer keeps up
Unstructured code, few or no tests, a data model that is hard to change.
A database migration
Moving from MongoDB to PostgreSQL, or restructuring a data model, without interrupting service.
A platform with several domains
Several business domains, roles, moderation or large imports living together in one API.
Scope of work
What we build.
An API is judged by what it lets you change without breaking the apps that use it.
NestJS architecture
Business modules, dependency injection, decoupled controllers and services, conventions shared by the team.
Data
PostgreSQL data models, Prisma, versioned migrations, and MongoDB when the use case justifies it.
API contracts
REST APIs documented with OpenAPI, controlled versioning, contracts shared with client apps.
Authentication and payments
Accounts, roles, OAuth, AWS Cognito, Stripe payments and webhooks.
Real time
WebSocket and notifications for messaging, auctions or live progress tracking.
Testing and quality
Unit and integration tests, continuous integration, tracked coverage. Blisterr's back end has 6,680 tests and 97% coverage.
Method
From the first route to production.
- 01
Model
Business domains, data model and API contracts, approved with the teams that consume the API.
- 02
Lay the foundations
Module structure, authentication, conventions, tests and continuous integration.
- 03
Deliver in increments
Features delivered with their tests and documentation, with code review at every step.
- 04
Operate
Deployment, monitoring, logs and procedures, by the team that wrote the code.
Responsibilities
Who decides what.
A typical division of responsibilities, agreed for each engagement.
| Topic | Your team | Black Tide |
|---|---|---|
| Business rules | You provide them and settle edge cases | We turn them into a model and an API |
| API contracts | Your client teams approve the contracts | We document and version them |
| Data | You remain the owner of the data and databases | We design the model and the migrations |
| Code review | Your process applies | We review and submit for review |
| Production | You decide on releases | We deploy and monitor |
Selected work
Node.js back ends in production.
Blisterr
NestJS back end being migrated from MongoDB to PostgreSQL 17 with Prisma, table by table and without downtime; 6,680 tests and 97% coverage.
Read the Blisterr caseFantasy Alley
NestJS API with around twenty business modules, PostgreSQL and AWS Cognito: self-publishing for authors and trust-based moderation.
Read the Fantasy Alley caseEach case describes the work delivered, its scope and the current status of the product.
Budget and next steps
Fixed price or time and materials.
Fixed price
For a defined NestJS or Node.js product or increment: discovery sets the scope, the estimate and the delivery increments.
Time and materials
A senior back-end engineer joins your team at our public day rate of €750 excl. VAT, for a short or long engagement.
Takeover
For an existing back end: a diagnostic of the code, data and operations, then stabilisation or a progressive migration.
Orders of magnitude
Budget ranges by maturity level, from prototype to scalable product, are published on our pricing page.
Useful questions
Frequent questions about NestJS and Node.js.
NestJS or Express?
Express leaves the whole structure to build; NestJS brings modules, dependency injection and conventions that help a team grow. For an API meant to last, we generally recommend NestJS.
PostgreSQL or MongoDB?
PostgreSQL for most products, as soon as relationships and data integrity matter. MongoDB remains relevant for some document-oriented uses. On Blisterr, we are migrating from MongoDB to PostgreSQL table by table.
Can you take over an existing API?
Yes. We first examine the code, data model, tests and deployment, then propose a step-by-step path rather than a rewrite.
Do you work with other back ends?
Yes: Java, Python, C# or C++ depending on the context. NestJS remains the foundation of most of our published projects.
Next step
Let’s talk about your back end.
The apps that consume the API, the data and the deadline: that is the starting point.