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How to choose architecture for a highload web or mobile project

How to choose architecture for a highload web or mobile project

Modern web and mobile projects are becoming increasingly complex. Even relatively small CRM systems, mobile apps, SaaS platforms, AI services, and marketplaces today handle large data flows, dozens of integrations, real-time events, and high workloads.

Against this backdrop, the term “microservices architecture” has practically become a marketing buzzword. Many clients are convinced that microservices alone automatically make a system scalable, modern, and capable of handling high loads. But in practice, this is far from always the case.

Moreover, a premature transition to microservices very often leads to:

  • complicated development;
  • budget overruns;
  • complex DevOps;
  • data synchronization issues;
  • slower releases;
  • increased technical debt.

At the same time, a huge number of modern high-load systems operate successfully based on:

  • monoliths;
  • modular monoliths;
  • asynchronous processing;
  • reactive programming;
  • WebSocket;
  • message queues;
  • Redis and CDN;
  • container infrastructure.

And only when there is a real need do individual parts of the system begin to be separated into microservices. The main goal of good architecture is not to be “trendy,” but rather to:

  • align with the current stage of the business;
  • handle the projected load;
  • remain manageable;
  • allow the system to scale gradually.

In this article, we will examine the main types of architectures, their differences, and use cases.

Simple architectures

Monolith

A classic monolith is an architecture where backend, frontend, business logic, and database run as a single application. Despite the popularity of microservices, the monolith remains one of the most widely used architectures in the world.

A monolith is well-suited for:

  • CRM and ERP systems;
  • enterprise platforms;
  • marketplaces;
  • SaaS MVPs;
  • B2B services;
  • most medium-sized web projects.

The main advantage of a monolith is simplicity:

  • easier development;
  • faster launch;
  • lower maintenance cost;
  • simpler testing;
  • less DevOps complexity.

It is important to understand: a monolith does not automatically mean poor performance. A modern monolith can serve tens or even hundreds of thousands of users with proper infrastructure design.

Headless monolith (REST API)

The next stage of evolution is headless architecture. In this case, the backend acts as a REST API:

  • frontend exists separately;
  • mobile applications use the same API;
  • frontend and backend are deployed independently.

For example:

  • backend in Java, Python, or PHP;
  • frontend in React or Vue;
  • mobile in Flutter or native.

Today, the headless approach has become the standard for most modern:

  • mobile apps;
  • PWA;
  • e-commerce projects;
  • CRM and ERP;
  • AI services;
  • Telegram Mini Apps.

This approach allows a single backend to serve both web and mobile platforms.

Modular monolith

A modular monolith is one of the most underrated architectural approaches. The system remains a monolith but is internally divided into independent modules:

  • CRM;
  • billing;
  • AI;
  • analytics;
  • notifications;
  • integrations;
  • realtime components.

At the same time:

  • the application remains a single unit;
  • the database can be shared;
  • releases remain centralized;
  • maintenance is simpler than in microservices.

A modular monolith is often the optimal choice for:

  • SaaS platforms;
  • enterprise systems;
  • CRM and ERP;
  • AI platforms;
  • high-load backends.

In many cases, it helps avoid premature microservices adoption.

Multithreading monolith

Multithreading is the next level of monolith optimization. The idea: multiple threads run inside a single application and process tasks in parallel.

For example:

  • API request handling;
  • report generation;
  • file processing;
  • background tasks.

This significantly improves performance without moving to a distributed architecture.

It is especially widely used in:

  • Java backends;
  • realtime processing;
  • queue and worker systems;
  • high-load systems.

Scalable monolith

A very common myth: a monolith cannot scale. In practice, a scalable monolith is one of the most common approaches in high-load systems.

How it works:

  • multiple instances of the application are launched;
  • a load balancer is placed in front;
  • traffic is distributed across servers;
  • database and cache run separately.

This allows a monolith to:

  • scale horizontally;
  • handle high traffic;
  • serve a large number of users.

In many cases, this is more than enough even for large projects.

Caching

A very common bottleneck in high-load systems is not architecture but lack of caching. Proper caching can reduce load on backend and database significantly.

Most commonly used:

Today Redis is used not only as a cache but also as:

  • realtime storage;
  • pub/sub system;
  • queue storage;
  • session storage.

In many projects, proper caching brings more benefit than complex architecture.

CDN

A CDN (Content Delivery Network) is another key element of modern infrastructure.

Cloudflare, CloudFront, and other CDNs allow:

  • faster frontend loading;
  • reduced latency;
  • content delivery closer to users;
  • reduced server load.

For international projects, CDN is especially important because content can be served from different regions:

  • Europe;
  • USA;
  • Asia;
  • Middle East.

HighLoad architectures

Asynchronous Programming

Asynchronicity is one of the key tools in high-load backend systems. The idea: the application does not block the main thread while waiting for operations.

For example: instead of executing multiple API requests sequentially, the system runs them in parallel.

This is especially important for:

  • AI integrations;
  • external APIs;
  • realtime systems;
  • file operations;
  • high-load backends.

Popular technologies:

Asynchronicity can significantly speed up even a monolithic application.

Reactive Programming

Reactive Programming is the next stage in the evolution of high-load systems. Here, the architecture is built around data streams.

Components:

  • subscribe to events;
  • react to changes;
  • process data asynchronously;
  • work in parallel.

Reactive architecture is especially suitable for:

  • AI;
  • realtime analytics;
  • monitoring systems;
  • IoT;
  • trading platforms;
  • event-driven systems.

Reactive programming can also work very well with monolithic architectures.

Real-Time Architecture (WebSocket + Reactive Programming)

Realtime systems are widely used today:

This is implemented using WebSocket connections.

WebSocket allows:

  • persistent connections;
  • instant event delivery;
  • minimal latency;
  • real-time communication.

Realtime architecture is often built on a combination of:

  • WebSocket;
  • reactive programming;
  • async processing;
  • data streams.

The application can still remain a monolith.

Queue and Worker Architecture

Message queues are one of the most important elements of high-load systems.

They allow:

  • buffering load;
  • executing background tasks;
  • offloading the backend;
  • processing heavy operations asynchronously.

Popular technologies:

This approach is especially important for:

  • AI processing;
  • email and push notifications;
  • document generation;
  • video/audio processing;
  • background jobs.

Even a monolith with queues can handle high load efficiently.

Container Architecture

The next stage is container-based architecture. The system is split into separate containers:

  • backend;
  • AI modules;
  • queues;
  • frontend;
  • realtime modules;
  • worker services.

Common tools:

The key advantage: each module can be scaled independently. At the same time, the system can still remain a modular monolith.

Microservices Architecture

Microservices represent a distributed architecture.

In this case:

  • the system is split into independent services;
  • each service has its own responsibility;
  • services communicate via APIs or message brokers;
  • different services may use different technologies.

Microservices are useful when:

  • the project becomes very large;
  • development teams grow significantly;
  • components require independent scaling;
  • complex distributed infrastructure emerges.

However, this comes with complexity:

  • distributed transactions;
  • observability;
  • monitoring;
  • service discovery;
  • network overhead;
  • distributed debugging.

So microservices are not “an improved monolith”, but a different level of engineering complexity.

MDA/EDA in Microservices

The next level of high-load architectures is Event-Driven Architecture (EDA). Here services interact through:

  • events;
  • message brokers;
  • data streams;
  • event queues.

This approach is widely used in:

  • fintech;
  • trading;
  • IoT;
  • AI systems;
  • enterprise integration;
  • realtime platforms.

It enables:

  • highly scalable systems;
  • load distribution;
  • loosely coupled services;
  • efficient realtime event handling.

However, this is already complex enterprise architecture requiring strong DevOps and high engineering maturity of the team.

Practical approach to architecture development

In practice, most successful projects follow a path similar to this:

Phase 1 – Monolith / Headless Monolith

Phase 2 – Modular Monolith

Phase 3 – Asynchronous Processing + Queues + Redis + WebSocket

Phase 4 – Container Architecture

Stage 5 – Selective Microservices

Stage 6 – EDA/MDA Distributed Systems

This approach allows you to:

  • avoid overspending at the start;
  • quickly launch an MVP;
  • gradually scale the system;
  • maintain architectural manageability.

How architecture affects the cost of a project

Architecture directly impacts:

  • the budget;
  • development timelines;
  • maintenance costs;
  • DevOps;
  • scalability;
  • release speed;
  • team costs.

For example: a small SaaS application built on microservices can cost several times more than a similar modular monolith solution.

And businesses don’t always need that level of complexity right from the start.

Conclusion

Modern high-load architecture isn’t just a race toward microservices.

In many cases:

  • modular monolith;
  • asynchronous processing;
  • reactive programming;
  • WebSocket;
  • Redis;
  • message queues;
  • container architecture

allow you to build a high-performance system without prematurely transitioning to a distributed architecture.

The primary task of a good engineering team is to select an architecture that aligns with:

  • the current stage of the business;
  • the load;
  • the budget;
  • the product development pace;
  • the scaling strategy.

This is precisely why the most effective architectures today are built not based on “trends,” but on the actual requirements of a specific project.

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