The frontend needs a backend
Turn an existing web or mobile experience into a connected product with APIs, data, authentication, admin support, and production delivery.
Backend Development Services
Backend Systems, APIs & Cloud Integrations Built Around Your Product
Digital Sensei designs and builds backend systems that connect product workflows, users, data, and external services—from APIs and databases through integrations, production deployment, and ongoing evolution.
Node.js + NestJS + Express
REST APIs + Data
Integrations + Cloud
Make the systems behind your product easier to trust, operate, and extend.
We look beyond endpoints and database tables to understand business rules, users, workflow states, data relationships, API consumers, external systems, and the way the product needs to evolve.
Business rules are hard to maintain
Reshape scattered conditions and workflow states into backend logic that reflects how users, operators, and the business actually work.
Roles and permissions are fragmented
Clarify authentication, user roles, permissions, sessions, and administrative boundaries across connected applications.
Systems need to communicate
Connect payments, notifications, telephony, AI services, devices, and third-party platforms through purposeful integration workflows.
The original model no longer fits
Improve data models, service structure, APIs, or fragile integrations incrementally when a full rewrite is neither necessary nor practical.
Delivery needs more structure
Make application configuration, hosting decisions, deployment, troubleshooting, and post-launch support part of one practical delivery path.
Backend application development across logic, APIs, data, access, integrations, and delivery.
Each technical choice follows the product workflow, operating constraints, integration requirements, and the teams and applications that will consume the backend.
Backend Application Development
Node.js, Express, and NestJS services for business logic, workflow orchestration, administrative operations, and backend application development.
REST API Development
Structured endpoints for React, Next.js, React Native, service integrations, and documented API contracts where appropriate.
Data & Database Engineering
PostgreSQL and MongoDB data modeling shaped around relationships, transactions, evolving structures, and query requirements.
Authentication & Access Control
Authentication, sessions and access patterns, user roles, permissions, and appropriate boundaries for customers, teams, and administrators.
Third-Party Integrations
Payments, notifications, AI, Voice AI, telephony, devices, business services, and custom third-party API integration.
Cloud & Production Delivery
AWS, DigitalOcean, Vercel where suitable, and Linux/Nginx configuration, deployment, troubleshooting, and infrastructure assistance.
Real product evidence across platform architecture, integrations, workflows, and data.
These products required different backend decisions. Together, they show how Digital Sensei connects business rules, users, data, external services, web and mobile applications, and production delivery.
Flagship backend platform
Synqro.ai
A React-based SaaS product with a structured NestJS backend, PostgreSQL-backed application data, backend APIs, users and organizations, role-aware workflows, authentication and session architecture, reporting, and admin and customer-facing applications.
Conversational workflows connect with Retell AI, and the system has been prepared for production deployment without separating the integration work from the wider product architecture.
NestJS • PostgreSQL • REST APIs • Roles • AI Integrations
Voice integration orchestration
HeyLibby
A 24/7 AI voice agent and virtual receptionist whose backend workflows coordinate phone conversations, business and service answers, requirement gathering, lead qualification, booking, multilingual voice experiences, and human handoff.
Twilio • OpenAI • Deepgram • ElevenLabs • Voice Workflow Integration
Order and payment lifecycle
Delimed
A Paris medicine-ordering platform connecting customer, pharmacy, and administrative workflows. Its backend supports prescription and non-prescription requests, pharmacy pricing, customer approval, Stripe capture after approval, pickup or delivery, and web/mobile API consumers.
Node.js • APIs • Stripe • Multi-role Workflows • Web + Mobile
Anleggsauksjon · Norway
Auction Portal
Anleggsauksjon is an operational equipment auction platform serving the Norwegian market. Its backend coordinates configurable category and listing forms, auction state, bidding and maximum auto-bids, outbid notifications, highest-bidder handling, and operator commission processes.
Node.js • Marketplace Logic • Auto-Bidding • Notifications • Configurable Workflows
Connected data workflows
Collab Care
A Canadian care-management SaaS with onboarding, centralized care records, configurable questions and workflows, patient history, care-team operations, wearable and sensor integration, monitoring, and threshold alerts. Its backend behavior continues to evolve with the product.
MERN • Data Workflows • Integrations • Monitoring • Alerts
Architecture should reflect the product—not force every product into the same stack.
Product workflows, data relationships, API consumers, integration requirements, maintainability, and operating constraints determine the appropriate boundaries and technology choices. The layers below show the areas we connect; they are not a mandatory stack for every project.
Web, mobile, and administration
React, Next.js, React Native, admin portals, and customer applications consume dependable backend capabilities.
Services and business logic
Node.js provides the runtime and ecosystem; Express suits flexible, lightweight services, while NestJS suits products that benefit from stronger modular structure and dependency organization.
Models, identity, and permissions
PostgreSQL is a strong fit for relational structure, transactions, and structured queries. MongoDB is useful when document-oriented flexibility better suits evolving domain data. Neither is universally better.
Integrations and production
Payments, notifications, AI, voice, telephony, and third-party platforms connect to production delivery on AWS, DigitalOcean, Vercel, or Linux/Nginx where appropriate.
Connect external services to complete business workflows.
API integration is more than sending a request. We account for authentication, data mapping, workflow synchronization, failures, appropriate retry behavior, state management, and the outcome users need to see.
Payments & notifications
Stripe payment workflows, email and application notifications, and business rules that keep user-facing and operational states aligned.
Telephony & Voice AI
Verified experience connecting Twilio, Retell AI, Deepgram, and ElevenLabs to phone, streaming, conversational, booking, qualification, and handoff workflows.
AI services
OpenAI and other verified AI service integrations connected to appropriate product context, backend rules, application data, and user workflows.
Devices & business platforms
Sensor and wearable integrations, external business systems, and custom third-party APIs with careful data and state mapping.
Custom REST APIs
Purpose-built API development for web, mobile, admin, partner, and system-to-system consumers, with clear contracts and maintainable service boundaries.
Integration continuation
Assessment and improvement of inherited or fragile integrations, including error handling, workflow clarity, and feature continuation without assuming a rewrite.
Already have the frontend or mobile app?
Digital Sensei can take responsibility for backend engineering as a defined technical workstream. You do not need to hand over the entire frontend project.
Digital agencies and technology partners can also engage Digital Sensei for backend, API, or integration capability when an additional engineering workstream is required.
Connect the existing product experience
- A React or Next.js frontend that needs an API and application layer
- A React Native application that needs backend services and data
- Authentication, roles, permissions, and administrative support
- Notifications, payments, AI, telephony, and external integrations
- Cloud configuration and deployment for the connected application
Strengthening an existing backend starts with assessment.
We first identify product priorities, existing constraints, operational risk, service and data boundaries, and what can be improved safely. A rewrite is not the default recommendation.
The practical path may be incremental: stabilize an integration, clarify API behavior, improve a data model, reorganize selected services, or introduce NestJS gradually where its structure provides real value.
Modernization can include
- Inherited Node.js or Express applications and partially built APIs
- Backend/API continuation and unstructured service-layer improvement
- Database and model improvements aligned with current requirements
- API cleanup and authentication or role improvements
- Fragile third-party integration and notification workflow improvements
- Deployment modernization, feature continuation, and ongoing support
Move from working backend code to an appropriately configured production application.
Cloud delivery stays connected to application requirements. Digital Sensei has practical deployment exposure across AWS, DigitalOcean, Vercel, Linux, and Nginx, selecting services according to the product rather than prescribing one platform.
Production configuration
Application and environment configuration, frontend/backend hosting decisions, and release preparation appropriate to the system.
Deployment setup
Application process deployment and practical delivery to AWS, DigitalOcean, or Vercel where the chosen architecture makes them suitable.
Domains, HTTPS & proxying
Domain and HTTPS configuration plus Linux/Nginx reverse-proxy setup where relevant to the production environment.
Ongoing assistance
Deployment troubleshooting, infrastructure assistance, backend maintenance, and continued product engineering after launch.
A connected path from product workflow to production support.
Architecture, backend engineering, frontend/mobile integration, QA, deployment, and ongoing support stay aligned around the product requirements.
Discover
Understand product workflows, API consumers, data, existing systems, constraints, and integration requirements.
Architect
Define service boundaries, data models, API contracts, roles, integrations, and suitable technology choices.
Build
Implement backend application logic, REST APIs, authentication, access control, and data workflows.
Integrate & QA
Connect external systems and validate end-to-end workflows across frontend, mobile, backend, and integration boundaries.
Deploy
Configure and release the application into the production environment appropriate to its architecture.
Support & Evolve
Maintain, troubleshoot, improve, and extend backend capability as the product and business requirements evolve.
Backend engineering grounded in business and product reality.
A backend development company should understand what the system must enable, not only the code it must contain. Digital Sensei can coordinate architecture, backend engineering, frontend/mobile integration, QA, DevOps, deployment, and ongoing support around the actual engagement.
Business-first architecture
Business rules, users, roles, states, data relationships, integration requirements, and operating constraints shape the backend design.
Connected product understanding
Experience across React, Next.js, React Native, backend services, data, and administration helps keep APIs aligned with the experiences consuming them.
Real integration delivery
Verified work spans payments, notifications, AI, voice, telephony, wearables, sensors, and external platforms in functioning product workflows.
Structured data and workflow thinking
Backend decisions stay connected to lifecycle states, permissions, relationships, transactions, reporting needs, and future change.
Senior technical involvement
Important requirements, architecture decisions, and technical risks remain close to experienced technical leadership throughout delivery.
Production and post-launch support
Deployment, issue resolution, modernization, infrastructure assistance, and continued backend development can follow the first release.
Questions about backend systems, APIs, databases, integrations, and delivery.
What backend technologies does Digital Sensei work with?
Digital Sensei works with Node.js, Express, NestJS, REST APIs, PostgreSQL, and MongoDB, alongside authentication, integration, deployment, and web/mobile application technologies. The stack is selected around the product requirements.
Do you build REST APIs?
Yes. We build custom REST APIs for web applications, React Native apps, admin portals, external services, and system-to-system communication.
Can you build a backend for an existing React or React Native application?
Yes. Backend engineering can be a defined workstream covering APIs, data models, authentication, admin support, notifications, integrations, and cloud deployment without requiring ownership of the entire frontend.
Do you work with Node.js and NestJS?
Yes. Node.js is part of our backend development ecosystem, and we use NestJS where its modular organization and maintainable application structure suit the product.
When would you use Express versus NestJS?
Express can be a strong choice for flexible, lightweight Node.js APIs and application services. NestJS can suit products that benefit from stronger modular structure, dependency organization, and architectural conventions. Neither is an automatic choice.
Do you work with PostgreSQL and MongoDB?
Yes. PostgreSQL is often a strong fit for relational data, transactions, important relationships, and structured querying. MongoDB can suit domains where document-oriented flexibility and evolving structures are useful.
Can you integrate third-party APIs?
Yes. Integration work can cover authentication, data mapping, workflow synchronization, state management, failures, appropriate retries, and clear user-facing outcomes.
Can you integrate Stripe or other payment workflows?
Yes. Digital Sensei has verified Stripe integration experience, including Delimed's approval-before-capture ordering workflow. The exact payment design depends on the product and provider requirements.
Can you integrate AI or Voice AI services into an existing backend?
Yes. Verified experience includes OpenAI, Retell AI, Twilio, Deepgram, and ElevenLabs integrations connected to real conversational, qualification, booking, training, and handoff workflows.
Can you work on an existing Node.js backend?
Yes. We can assess inherited Node.js or Express applications, partially built APIs, service layers, integrations, data models, and deployment arrangements before defining the next useful work.
Do you recommend rewriting an existing backend?
Not automatically. We assess the codebase, risks, product priorities, constraints, and operating needs first, then modernize incrementally where that is the safer and more practical path.
Can you handle authentication and role-based access?
Yes. Backend work can include authentication, session and access patterns, user roles, permissions, and administrative boundaries appropriate to the product, without publishing sensitive implementation details.
Can you deploy the backend to AWS or DigitalOcean?
Yes. Digital Sensei can assist with application deployment and production configuration on AWS or DigitalOcean, and with Vercel, Linux, or Nginx where appropriate to the system.
Do you provide ongoing backend support after launch?
Yes. Support can cover maintenance, production issue resolution, integration troubleshooting, feature development, backend modernization, infrastructure assistance, and continued product evolution.
Need a backend your product can depend on?
Share the product workflow, frontend or mobile application, or existing backend you need to build, integrate, or improve. Digital Sensei can help define a practical architecture and delivery path.