Is Event Sourcing Right for Your Project? Use these 4Cs to Decide
Where should you apply event sourcing? While this architectural pattern works well for applications of all sizes, beginners should choose projects that maximize their return on investment. Here are four practical rules I use to determine whether event sourcing is a good fit for a project.
Quick Rule of Thumb: The 4Cs
From my experience, event sourcing is most effective when applied to applications that participate in the business’ core operations. This means processes with huge strategic value that can make or break the business.
A quick way to identify these processes is to look for characteristics I call the 4Cs:
- Collaborative – Involve multiple parties and systems
- Compliant – Satisfy rules and regulations
- Causal – Have outcomes that depend on past actions
- Changing – Frequently adapt to market conditions
1. Collaborative: Involve Multiple Parties and Systems
Collaborative processes involve many parties, such as customers, staff, and systems, all working toward a shared goal: from delivering a lunch order to coordinating a national vaccination rollout.
Event sourcing fits because the shared event log becomes a single source of truth across all teams. When something looks wrong, say a vaccine batch appears delivered twice, you can trace the sequence of events and reconcile quickly.
The more stakeholders who care about and depend on the history of a given process, the more valuable event sourcing becomes. Picture a branching tree of people, teams, and systems connected to the work – bigger tree, bigger payoff. A car sale signing, for example, triggers accounting, inventory, service, and finance activities. By contrast, a purely personal task like updating your own to‑do list offers little shared value, so event sourcing would just add overhead.
2. Compliant: Satisfy Rules and Regulations
Compliant processes must satisfy external mandates such as SOX for finance, HIPAA for health data, PCI DSS for payment card data, and internal audit requirements.
Event sourcing helps by producing an immutable timeline of every action: what happened, when, and by whom. When someone asks, “Who accessed this record?” or “Show the approval chain for this $50M trade,” the log can answer directly.
Beyond regulations, event sourcing is also effective for internal business policies like approval workflows, expense authorization chains, or quality control procedures that require clear accountability and process documentation.
3. Causal: Have Outcomes That Depend on Past Actions
Causal processes are those where current outcomes depend strongly on prior events, for example: credit scoring from payment history, insurance pricing from claims, or recommendations from past behavior.
Event sourcing helps by retaining the full event sequence behind any state. You can replay to explain a decision, recalculate with new rules, or analyze patterns. If you ask, “Why was this loan approved?” or “How was this price set?” the log shows the chain.
Processes that only need current state - who’s online, today’s weather, simple email format checks - might not benefit much from event sourcing’s causal capabilities.
4. Changing: Frequently Adapt to Market Conditions
Changing processes are those that need to evolve rapidly in response to market conditions, customer feedback, or business requirements. Think dynamic pricing algorithms that adjust based on demand, personalized marketing campaigns that adapt to user behavior, or supply chain logistics that respond to real-time disruptions.
Event sourcing excels in changing environments because it provides flexibility to adapt without losing historical context. You can replay past events with new business rules, migrate data models without losing information, or add new features that analyze previously ignored patterns. When requirements change, say you need to calculate customer lifetime value differently or implement new fraud detection rules, you can apply these changes retroactively to your entire event history.
At the same time, the event log can quickly be projected to any database model in any schema for any team, allowing the business to evolve rapidly without being locked into a legacy data model.
How to Score Your Process
To apply these rules practically, score each of your candidate processes on a scale of 0-2 for each C: 0 (absent), 1 (moderate), 2 (strong). A process scoring 6-8 total is likely a great fit for event sourcing, while anything below 3 probably isn’t worth the complexity. Focus your pilot on the highest-scoring process.
Next Steps
Event sourcing isn’t a universal solution, but when applied strategically to processes that are Collaborative, Compliant, Causal, and/or Changing, it becomes a competitive advantage. The 4Cs help you cut through the hype and focus on domains where the event log becomes genuinely valuable, not just another database.
Start small with your highest-scoring process, model a handful of business events, and validate that you can answer questions you couldn’t before. The payoff comes not from the technology itself, but from choosing the right problem to solve. Use the 4Cs as your filter, and event sourcing becomes a strategic tool rather than an architectural experiment.