# Backend Development & API Engineering

> Backend development services: typed APIs, sound data models, and services engineered for integrity and scale. Node and Python backends by Sentient Arc.

The system of record and the contracts around it: typed APIs, sound data models, and services engineered for integrity and scale, because the data outlasts every UI.

## The schema is the decision you cannot undo
Interfaces get redesigned every couple of years; the data model underneath them is forever. A shortcut in the schema or the API contract compounds quietly until it is load-bearing and unmovable.

The failures that hurt most live here: the lost write, the race condition, the report that is subtly wrong, the endpoint that buckles at ten times the traffic. None of them show up in a demo.

## Contracts first, then throughput
We design the data model and the API contract before the throughput problem exists: normalized where it matters, typed at the boundary, and explicit about the invariants the business depends on.

Scale is engineered deliberately, not guessed: indexing, caching, queues, and idempotent operations added where load and correctness demand them, with the numbers to justify each one.

## What we build
- **APIs & service contracts**: Typed REST or GraphQL APIs with versioning and validation, designed to absorb the roadmap instead of resisting it.
- **Data models**: Schemas designed for integrity and query patterns you actually have, so the data stays trustworthy as it grows.
- **Scale & reliability**: Indexing, caching, queues, and idempotency added where load and correctness require them, backed by measurement.
- **Integrations & auth**: Third-party services, webhooks, and auth boundaries wired in with retries, audit trails, and least privilege.

## Stack
- **Runtime:** Node.js, Nest.js, Express.js, Python, Django
- **Data:** Postgres, Redis, Prisma, Queues
- **Ops:** REST & GraphQL, Observability, AWS, CI/CD

## FAQ
**What do your backend development services cover?**

API design, data modeling, integrations and auth, and the reliability engineering (indexing, caching, queues, idempotency) that keeps a system correct and fast under real load.

**REST or GraphQL, SQL or NoSQL?**

Decided by the data and the access patterns, not by fashion. Postgres and REST are our defaults because they fit most products; we reach for GraphQL or other stores when the shape of the problem earns it.

**Can you scale a backend that is already struggling?**

Yes. We profile first to find the real bottleneck, the query, the missing index, the N+1, the hot lock, then fix it, rather than throwing infrastructure at a symptom.

**Do you build backends for a frontend another team owns?**

Yes. We deliver a documented, typed API a separate frontend or mobile team can consume cleanly, with the contract as the shared source of truth.

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Canonical page: https://www.sentientarc.com/capabilities/backend-development