How is scalability taken into account during construction?

Oscar Bout · 15 Aug 2026

Scalability is built into software by making deliberate architectural choices during the design phase. Think about dividing the application into separate components, choosing the right database structure, and planning how the software can handle more users without performance degrading. The sections below answer the most frequently asked questions about scalability during software development.

Which architectural choices determine the scalability of software?

The scalability of software is largely determined by the chosen architecture. The two most decisive choices are: working with a monolithic architecture or with a microservices architecture. With microservices, the application consists of separate, independent services that can each be scaled individually. This makes it much easier to scale only the components that need it.

Other architectural choices that directly affect scalability:

Stateless application design: servers do not store user sessions locally, allowing you to easily run multiple servers side by side
Asynchronous processing: time-consuming tasks are processed in the background via a queue, so the user does not have to wait
API-first design: functionality is exposed through clear interfaces, allowing components to grow independently of each other
Use of cloud platforms: platforms such as AWS and Azure offer built-in scalability tools that you can deploy immediately

The architectural choice at the beginning of a project has major long-term consequences. An application that needs to be made scalable later costs considerably more time and money than one that is built that way from the start.

How is scalability built in during the design phase?

Building scalability into the design phase means thinking about how the application will grow before writing the first line of code. You do this by defining expected user numbers, data volumes, and peak loads, and aligning the architecture accordingly. This prevents you from having to lay the foundation all over again later.

Concrete steps taken during the design phase:

Capacity planning: determine how many users the application needs to handle now and in the future
Bottleneck analysis: identify which parts of the application will come under pressure first
Modular design: split functionality into separate modules that can be extended independently of each other
Caching strategy: determine which data can be cached to reduce the load on servers and databases
Technology stack selection: choose technologies that demonstrably perform well under high load, such as NodeJS, Java, or .NET

A good design saves a lot of time later. Teams that address scalability only after the fact run into fundamental limitations that cannot easily be resolved without rewriting large parts of the application.

What is the difference between vertical and horizontal scaling?

Vertical scaling means making an existing server more powerful by adding more memory, CPU, or storage. Horizontal scaling means adding more servers that handle the load together. The key difference is that vertical scaling has a physical ceiling, while horizontal scaling can in principle be expanded indefinitely.

A comparison makes the difference clear:

Vertical scaling: quick to implement, no code changes required, but more expensive with significant growth and limited by hardware constraints
Horizontal scaling: more flexible and cost-effective at scale, but requires the application to be stateless and load balancing to be properly configured

In practice, most scalable applications combine both methods. During a sudden peak load, a server can temporarily receive more resources, while long-term growth is accommodated by adding extra servers. Cloud platforms such as AWS and Azure make it possible for this to happen automatically based on current usage.

How is load balancing applied in scalable software?

Load balancing automatically distributes incoming requests across multiple servers, so that no single server becomes overloaded. A load balancer sits between the user and the application servers and routes each request to the server with the most available capacity at that moment. This ensures stable performance, even during peak loads.

Load balancing works best when the application is stateless. This means that any server can handle the same request, regardless of which server a user used previously. Session information is then stored centrally, for example in a shared cache or database, so that all servers have access to the same data.

Popular forms of load balancing include:

Round-robin: requests are distributed in turn across the available servers
Least connections: the request goes to the server with the fewest active connections
IP-hash: a user is always routed to the same server based on their IP address

Cloud providers such as AWS and Azure offer built-in load balancers that automatically scale with the number of servers in your environment.

What role does the database play in the scalability of an application?

The database is often the first bottleneck as an application grows. A poorly designed database slows down the entire application, even if the servers are powerful enough. The scalability of the database depends on the chosen database technology, the structure of the data, and the way queries are constructed.

Relational versus non-relational databases

Relational databases such as PostgreSQL and MySQL are powerful for structured data and complex relationships, but scale horizontally less easily. Non-relational databases such as MongoDB or Cassandra are inherently better suited for horizontal scaling and large volumes of unstructured data.

Techniques to make databases scalable

Regardless of the chosen database, there are techniques that improve scalability:

Read replicas: read requests are distributed across multiple copies of the database
Sharding: data is split across multiple databases based on a partition key
Database caching: frequently used query results are temporarily stored in a fast cache such as Redis
Query optimization: well-indexed tables and efficient queries significantly reduce the load on the database

A solid database architecture is an investment that pays off as the application grows. Problems that arise at that point are difficult to resolve after the fact without downtime or major changes.

How is scalability tested before an application goes live?

Scalability is tested by exposing the application to simulated load that mimics the expected peak load. This is called load testing or stress testing. The goal is to discover where the application first breaks down, so those bottlenecks can be resolved before going live.

Commonly used testing methods include:

Load testing: tests how the application performs at the expected maximum number of concurrent users
Stress testing: tests what happens when the application is pushed beyond expected limits, so you know where the boundaries lie
Soak testing: tests how the application performs under sustained load over a longer period, to detect memory leaks or degradation
Spike testing: simulates sudden spikes in usage, such as during a marketing campaign or a viral post

Tools such as Apache JMeter, k6, and Locust are widely used for these tests. The results provide insight into response times, error rates, and database behavior under pressure. Based on these insights, adjustments are made before real users access the application.

How we help with scalable software development

At 3Bird, we build software that not only works today but also grows with your business. Scalability is not an afterthought, but a deliberate choice that we discuss with you from the very first conversations. Our approach combines Dutch quality standards with an experienced international development team, so you get high-quality software development at a rate that fits your budget.

What you can expect from us in terms of scalability:

We design the architecture together with you, based on your current and future needs
Our developers work with proven technologies such as AWS, Azure, NodeJS, React, Java, and .NET
We conduct load tests before going live, so you know how the application behaves under pressure
Through our fractional CTOs in the Netherlands, you always have a point of contact to guide you in your own language
You can easily scale your team up or down, with developers available from €25 per hour

Want to know how we build your application to scale? Contact us at contact@3bird.nl or call +(31)75-7993038 for a no-obligation conversation about your project.