You’ve heard the pitch for microservices. Small, independent services. Teams that can ship without waiting on six other teams to finish their sprint. No more three-month release cycles because somebody touched a shared library. It sounds great — and honestly, the core idea is great. But here’s the thing: a lot of teams adopt microservices and end up with something worse than the monolith they started with.
I’ve spent the most recent part of my career working with distributed systems, and I’ve seen some of the ways monolith-to- microservice transitions can go awry. A team takes their monolith, draws some boxes around the major modules, splits them into separate services, deploys them independently, and declares victory. Six months later they’re debugging cascading failures at 2 AM and wondering why everything is harder than it used to be.
What went wrong? They broke the monolith apart without actually decoupling it. And a distributed monolith — where you have all the operational complexity of microservices with none of the benefits — is arguably the worst of both worlds.
The Coupling Problem
Let’s be specific about what tight coupling looks like in a microservices architecture, because it’s not always obvious.
Synchronous request-response everywhere. Service A calls Service B, which calls Service C, which calls Service D. If any one of those services is slow or down, the whole chain stalls. You haven’t built a resilient distributed system — you’ve built a monolith with network hops. And network hops are the worst kind of function calls, because now you get to deal with latency, partial failure, and timeout tuning on top of everything else.
Shared databases. Multiple services reading from and writing to the same tables. This is the one that sneaks up on people, because the database feels like shared infrastructure rather than a coupling point. But the moment you need to change a schema, you’re coordinating across every service that touches those tables. You’re right back to “deploy everything together or deploy nothing” — which is exactly what microservices were supposed to fix.
Data format dependencies. Service A produces a message with a certain structure. Services B, C, and D all parse that structure. Now Service A needs to add a field or change a type. Congratulations, you need buy-in from three other teams before you can ship. That’s not independent deployment — that’s a distributed approval process.
Temporal coupling. Services that have to be running simultaneously to function. If the downstream service isn’t up right now, the upstream service can’t do its job. Your services aren’t really independent if they can only work when everyone else is awake. (Kind of like a group project where one person has to be physically present for anyone else to make progress. We’ve all been in that group project.)
If any of this sounds familiar, you’re not alone. And the good news is that these problems are well-understood, and there are well-established patterns for solving them.
Thinking in Events
Here’s the mental shift that makes the difference: stop thinking about services calling each other, and start thinking about services reacting to things that happen.
This is event-driven architecture, and at its core it’s about making your software reflect how the real world actually works. The real world doesn’t operate on synchronous request-response. Things happen — a customer places an order, a sensor reads a temperature, a payment clears — and other parts of the system respond to those events on their own terms, at their own pace.
When you build systems this way, something interesting happens to those coupling problems:
Synchronous chains disappear. Service A publishes an event. It doesn’t know or care who’s listening. Services B, C, and D each pick up the event and do their thing independently. If Service C is having a bad day, Services A, B, and D don’t notice — they keep right on working.
Data ownership becomes clear. Each service owns its data, publishes events about what changed, and subscribes to the events it cares about from others. No shared databases, no schema coordination nightmares.
Temporal coupling goes away. If a service is down when an event is published, that event waits in the stream until the service recovers and processes it. The system degrades gracefully instead of falling over.
Now, this isn’t magic — you’ve traded one set of challenges for a different set. Event-driven systems have their own complexities: eventual consistency, event ordering, debugging asynchronous flows. We’ll get into all of that. But at least these are the right problems to have — problems that come from genuinely decoupled services rather than from a distributed monolith pretending to be something it’s not.
Patterns That Make It Work
If you start exploring event-driven microservices, you’ll quickly run into a set of well-known patterns that have emerged to address the practical challenges. Chris Richardson’s microservices.io is an excellent catalog of these — I’d recommend bookmarking it.
Two patterns in particular are going to be central to what we explore in this blog:
Event Sourcing — instead of storing the current state of your data and updating it in place, you store the sequence of events that led to the current state. Every state change is captured as an immutable event in an append-only log. This gives you a complete, auditable history of everything that happened in your system — not just “the account balance is $500” but “here’s every deposit, withdrawal, and transfer that got it there.”
The appeal is obvious. The catch is also obvious — if you need the current state, do you really have to replay every event from the beginning of time? For a system that’s been running for years, that’s not just slow, it’s unworkable.
CQRS (Command Query Responsibility Segregation) — and this is where it gets interesting. You separate the write path (commands that produce events) from the read path (queries that serve up current state). The write side stores events. The read side maintains materialized views — pre-computed projections of whatever the read side needs, kept up to date by consuming the event stream.
Event sourcing gives you the complete, immutable history. CQRS and materialized views give you fast reads without replaying the entire event log every time someone wants to check a balance. They’re complementary patterns that address each other’s weaknesses, and together they form the backbone of a lot of well-designed event-driven systems.
What’s Ahead
This blog is going to be a hands-on exploration of these ideas — patterns first, then concrete implementations. In the posts to come, we’ll dig into:
- Resilience through decoupling — how event-driven systems degrade gracefully instead of cascading failures
- Auditability and replay — the power of an event log as a source of truth, not just for debugging but for compliance, analytics, and the ability to answer questions you didn’t think to ask yet
- Independent scalability — scaling the services under load without scaling everything, because your order processing pipeline doesn’t need to drag your user profile service along for the ride
- Evolvability — adding new consumers of existing events without touching the producers, so your analytics team can tap into a data stream without filing a ticket with the team that owns it
We’ll look at the patterns in general terms — what problem each one solves, what trade-offs it introduces, how to think about whether it’s the right fit — and then we’ll get into specific, working implementations that you can pull apart, run, and adapt to your own projects.
If you’re a developer who’s building or maintaining a microservices architecture and found it harder than expected — or if you’re designing a new system and want to avoid the common pitfalls — this series is for you. The patterns are universal; the implementations will be specific. Let’s see where it takes us.
Nodes and Edges 