april, 2025

Microservices vs Event-Driven Architecture: Which Scales Better in 2025?

If you're launching a digital product or upgrading an existing one, architecture is the foundation. The way you structure your system will determine how easily it scales, evolves, and handles future demands.

Today, teams often blend or emphasize one of two popular approaches: microservices (MSA) and event-driven architecture (EDA). Let’s explore how they work, their strengths and weaknesses, and how to pick the best fit for your business.

Microservices: for more control

Microservices split your system into separate modules: registration, payments, delivery, notifications — each one works independently and communicates through APIs.

Architecture is always a tightrope walk between control and flexibility. Microservices (MSA) shine because they neatly carve up logic, offer independent scaling, and make debugging a breeze. Each service stands on its own, owning a specific domain and chatting with others via APIs—usually REST or gRPC. Sounds like a dream setup, right? But here’s the catch: as services multiply, their connections grow complex. Hidden dependencies emerge—if one service tweaks its API, others must adapt. The result? Microservices can become so interdependent that your system turns into a “distributed monolith”—structured as separate services but behaving like a single, rigid system.

Take Amazon, for instance. They started with a monolith but shifted to microservices, enabling teams to build independent systems like product catalogs or checkout flows. Yet, this introduced challenges: for example, updating the API for their recommendation service often required coordinated changes across dozens of dependent systems, and API versioning demanded tight synchronization.

Business benefits:

New features can launch faster.
Teams can work in parallel without blocking each other.
If load increases, you can scale only the services that need it.

Things to consider:

The more services you have, the harder it is to manage their dependencies
A change in one service may require updates across the system.

Best for:

Systems with many third-party integrations.
Clear, step-by-step logic (like payments or user authentication).
Situations where predictable responses are critical.

Event-Driven Architecture: for more flexibility

Now, let’s flip the script and talk event-driven architecture (EDA). Instead of services pinging each other directly, they just fire off events.

Say a registration service broadcasts “user registered.” Subscribers decide how to react: one creates a profile in the database, another shoots off a welcome email, a third logs it in the CRM. The service that triggered the event? It doesn’t care who’s listening—it just drops the signal into a message bus (think Kafka, RabbitMQ, or Amazon EventBridge).

This setup brings a ton of perks. First, it scales like a champ: load gets spread out, and new subscribers can hop on without touching the original service. Second, it’s resilient—if one handler crashes, the events stick around and get processed later. Third, it’s perfect for async tasks. Picture e-commerce: an order’s placed, and the system handles notifications, payment deductions, and logistics in the background, no waiting required.

Netflix is a poster child for this. Their logging and monitoring systems lean on EDA—streaming, recommendations, billing, and analytics all swap events via Kafka, letting them scale dynamically under crazy loads.

But EDA has downsides. Debugging is trickier than with microservices: events flow asynchronously, making it hard to pinpoint where an issue arose—did an event vanish, or did a service fail? Tracing and monitoring are essential. Uber, for instance, uses OpenTelemetry and Jaeger to track events across hundreds of services.

Event management adds complexity. A single event, like “order placed,” can trigger multiple processes: notifications, payments, logistics. But network glitches might resend the event, and without deduplication or idempotency, you risk errors like charging a customer’s card twice. Airbnb ran into this scaling their booking system—they had to clamp down hard on reprocessing controls.

Business benefits:

Easier to scale — new features can be added without touching existing ones.
More resilient — the system keeps working even if one part fails.
Ideal for background tasks and automation (e.g., emails, reports, CRM updates).

Things to consider:

Requires more planning at the start.
Harder to debug — you need solid monitoring to trace issues.
Must handle duplicates and delays carefully.

Best for:

Growing platforms with lots of features and background operations.
High-load environments.
Projects where you want to stay flexible long-term.

So, what’s the play?

If your system craves tight sync and predictability, microservices are your go-to. If you’re chasing flexibility, resilience, and component independence, events win.
Realistically, though, the sweet spot’s a hybrid. Critical requests—like auth or payments—should stick to APIs to dodge delays and duplicates. For secondary stuff—notifications, analytics, third-party integrations—a message broker’s your friend.

Amazon’s marketplace nails this combo. Place an order via REST API for instant confirmation, while processing is event-driven for flexibility:

User submits order → order service saves it to the DB and confirms with the user.
“Order created” event hits the bus.
Payment service subscribes → charges the card.
Logistics service subscribes → pings the warehouse.
Notification service subscribes → emails the customer.

The takeaway? The bigger your system, the more events shine—but don’t ditch APIs entirely. The trick is not oversimplifying at the expense of scalability.

Our advice

Don’t choose architecture based on trends. Start with your business goals:

What do you want your system to handle in a year or two?
That answer will tell you which setup offers the most value.