Building Resilient Microservices: Lessons from the Banking Industry
As a Software Development Engineer at Lloyds Banking Group, I've had the opportunity to work with microservices architectures at scale. Financial institutions face unique challenges when it comes to system reliability—downtime isn't just an inconvenience, it can have serious financial and regulatory consequences.
In this article, I'll share some of the key patterns and practices we've implemented to build resilient microservices that can withstand various types of failures.
Circuit Breakers: Preventing Cascading Failures
One of the most important patterns we've implemented is the circuit breaker pattern. When a service dependency begins to fail, a circuit breaker can detect this and "trip," preventing further calls to the failing service. This stops the failure from cascading throughout the system.
We've found that implementing circuit breakers with configurable thresholds and half-open states allows us to gracefully handle temporary failures without requiring manual intervention.
Bulkheads: Isolating Failure Domains
Another critical pattern is the bulkhead pattern, inspired by ship design. By partitioning service instances and resources, we ensure that failures in one area don't sink the entire ship.
For example, we maintain separate connection pools for different types of database operations, ensuring that slow-running queries don't exhaust connection resources for critical, quick operations.
Lessons Learned
Building truly resilient systems isn't just about implementing patterns—it's about shifting how we think about failure. Here are some key lessons:
- Failure is inevitable—design for it rather than treating it as an exceptional case
- Test your resilience mechanisms regularly with chaos engineering practices
- Monitor not just services but also the health of your resilience mechanisms
- Document failure modes and recovery procedures for each service
These practices have helped us maintain high availability even during significant infrastructure events, and the principles apply across industries, not just in financial services.