Custom middleware development that connects your systems seamlessly
Building middleware with Appfront: we build the invisible connecting layer that makes your applications, databases and external services work together as one. From API gateways and message brokers to enterprise service buses and custom integration layers.
What is middleware and why do you need it?
Middleware is the software layer that sits between your applications, databases and external services. It translates, routes and transforms data so that systems never designed to work together can communicate seamlessly. Without good middleware, you end up with a tangle of point-to-point integrations that are fragile, unmanageable and hard to scale.
In practice, middleware is the backbone of every modern IT landscape. Whether you're building a web application that needs real-time data from your ERP, a mobile app that communicates with multiple back ends, or a microservices architecture where dozens of services exchange messages with one another, middleware makes it possible. We design and build this integration layer to measure, tailored to your specific systems landscape and growth ambitions.
From spaghetti to structure
Many organisations grow organically: system by system, integration by integration. The result is a tangled web of direct connections that break as soon as one system changes. Middleware centralises that communication. Each system only talks to the middleware, never directly to other systems. That makes changes, extensions and migrations considerably easier.
Our middleware specialisms
Middleware is a broad field. We focus on three core areas that together form the foundation of a robust integration layer. Every project starts with the question: which type of middleware solves your specific problem best? See also our wider API integration services.
API gateway development
An API gateway is the central access point for all your API traffic. It handles authentication, rate limiting, request routing and load balancing in a single place. We build API gateways on proven technology such as Kong or Nginx, or fully custom. This keeps you in control of who can request which data, how often, and with what authorisation. Ideal if you are building an API-first platform or want to expose multiple microservices externally through a unified interface.
- Central management of API authentication and authorisation
- Rate limiting and throttling per consumer
- Request and response transformation and validation
- Load balancing and failover routing
Message broker implementation
Message brokers enable asynchronous communication between systems. Instead of system A calling system B directly and waiting for a response, it places a message on a queue. System B processes that message when it is ready. We implement message brokers with Apache Kafka for high-throughput event streaming, RabbitMQ for reliable message queuing, or Redis Streams for lightweight pub/sub scenarios. The result: systems that scale independently and don't fall over when a downstream service is temporarily unavailable.
- Event streaming with Apache Kafka
- Reliable queuing with RabbitMQ
- Pub/sub patterns for real-time notifications
- Dead letter queues and retry mechanisms
Enterprise service bus (ESB)
An enterprise service bus is the most complete form of middleware: it combines message routing, protocol conversion, data transformation and service orchestration in one central platform. We build ESB solutions for organisations with complex systems landscapes where dozens of applications must communicate with one another. From enterprise software that communicates via SOAP to modern REST APIs and real-time event streams, the ESB translates, routes and monitors everything.
- Central orchestration of system communication
- Protocol conversion (REST, SOAP, GraphQL, gRPC)
- Content-based routing and filtering
- Transaction management across multiple systems
Where middleware makes the difference
Middleware is not an end in itself, but a means to solve concrete business problems. Below are four scenarios where custom middleware makes the difference. Want to know more about our approach to integrations? Take a look at our services or our previous work.
Legacy System Integration
Many organisations run on systems that have been reliable for years but were never built for modern integration. SOAP services that cannot communicate directly with REST clients. Mainframe systems that expect batch files instead of real-time API calls. We build middleware that acts as a translation layer: the legacy system remains untouched, while new applications interact with it through modern interfaces. This extends the lifespan of your existing investments without holding back innovation.
Microservices Communication
In a microservices architecture, each service communicates with several other services. Without middleware, you end up with an exponentially growing network of direct integrations. We implement service mesh solutions and sidecar patterns that handle communication, retry logic, circuit breaking and observability outside the application code. Your developers focus on business logic; the middleware takes care of communication.
Event-driven architecture
When systems need to respond to events directly (an order, a sensor reading, a status change), an event-driven architecture is the right choice. Middleware acts as an event bus: producers publish events, and consumers subscribe to the events relevant to them. We design event-driven systems using Kafka, RabbitMQ or cloud-native solutions that can handle millions of events per second without data loss.
Data Transformation and Synchronisation
Different systems speak different data languages. Your ERP works with XML, your webshop with JSON, your legacy system with CSV files. Middleware transforms data between all these formats, enriches it with additional context, validates it against business rules and routes it to the correct destination. We build transformation layers that combine protocol conversion (REST to SOAP, GraphQL to gRPC) and data mapping into a reliable, auditable pipeline.
Tools and Technologies
We choose technology based on your requirements, not on hype. Below are the tools and frameworks we use to build middleware, grouped by category. The choice depends on factors such as throughput requirements, the existing landscape, team expertise and budget. Also discover how we use platform engineering to keep your middleware infrastructure manageable.
API Gateways and Routing
- Kong Gateway (open-source and enterprise)
- Nginx and OpenResty for high-performance proxying
- AWS API Gateway and Azure API Management
- Traefik for container-native routing
- Custom gateways in Node.js, Go or Python
Message Brokers and Streaming
- Apache Kafka for event streaming and log aggregation
- RabbitMQ for reliable AMQP messaging
- Redis Streams and Redis Pub/Sub
- Amazon SQS, SNS and EventBridge
- NATS for lightweight, high-performance messaging
Orchestration and Integration
- Apache Camel for enterprise integration patterns
- Kubernetes with service mesh (Istio, Linkerd)
- gRPC for high-performance inter-service communication
- GraphQL Federation for API composition
- Temporal for workflow orchestration
Caching and Performance
- Redis for distributed caching and session stores
- Memcached for simple key-value caching
- Varnish for HTTP-level caching
- CDN integration for edge caching
- Cache invalidation strategies (TTL, event-based, write-through)
Test your idea first: a working prototype in 1 day
With OneDayBuild, we turn your idea into something tangible in one day for €1,150, so you can see whether further development is worth the investment. Decide to go ahead with the full build? Then we credit the full cost.
Explore OneDayBuild →Why Appfront for Your Middleware?
Building middleware requires a deep understanding of both the systems being connected and the patterns that make this reliable. We combine hands-on engineering with architectural expertise to build integration layers that not only work today, but also scale with your growth tomorrow.
Our philosophy
Good middleware is invisible. You only notice it when it's gone. We build integration layers that quietly do their job, day in, day out, without anyone having to give them a second thought.
Full-stack integration expertise
Middleware cannot be separated from the systems it connects. Our team builds both the applications and the integration layers between them. This means we understand the entire chain: from the database query in your custom software to the message arriving at an external system. That end-to-end knowledge prevents blind spots in the design.
- Experience with complex system landscapes
- Knowledge of both backend and infrastructure
- Protocol expertise: REST, SOAP, GraphQL, gRPC, WebSocket
Operational awareness
Middleware that works in development but falls over in production has no value. From day one, we think about operational matters: how do you monitor the middleware? What happens under peak load? How do you roll out updates without downtime? That operational awareness translates into middleware that is not only functionally correct, but production-ready. Read more about our approach.
- Built-in health checks and alerting
- Support for blue-green and canary deployments
- Graceful degradation and circuit breaker patterns
Security and performance
Middleware forms the nervous system of your IT landscape. That makes it both an attractive target and a potential bottleneck. We design middleware with security and performance as first-order requirements, not as an afterthought.
Security by design
Every request that flows through the middleware is authenticated, authorised and validated. We implement OAuth 2.0 and OpenID Connect for identity federation, mutual TLS for service-to-service communication, and input validation at every boundary. Audit logging records who requested what and when, giving you full traceability. Read more about our information security policy.
- OAuth 2.0, JWT and API key management
- Mutual TLS (mTLS) for internal communication
- Input validation and schema enforcement
- GDPR-compliant data handling
- Audit logging and access trails
- DDoS protection and rate limiting
Performance and observability
Middleware that adds latency to every request is worse than no middleware at all. We optimise for minimal overhead: connection pooling, efficient serialisation, caching at the right layers and asynchronous processing where possible. Distributed tracing with OpenTelemetry makes it possible to follow every request through the entire chain, from entry point to final destination.
- Distributed tracing with OpenTelemetry and Jaeger
- Centralised log management (ELK stack, Grafana Loki)
- Metrics and dashboards (Prometheus, Grafana)
- Connection pooling and keep-alive optimisation
- Horizontal scaling and auto-scaling
- Load testing and capacity planning
Frequently asked questions about building middleware
Ready to seamlessly connect your systems?
Whether you need an API gateway, want to set up an event-driven architecture, or need to expose legacy systems, we help you at every step. Explore our services, read more about us, or get in touch directly for a no-obligation architecture consultation.
Current context (May 2026)
According to Statistics Netherlands (CBS), Dutch SMEs are increasingly using cloud accounting packages with API integrations to webshops and CRM systems, a growth that has accelerated over the past five years.
Source: CBS — ICT use by businesses (www.cbs.nl)