Modernize Your Payment System with Microservices: Part 3 – Incorporating Resilience to Mitigate and Prevent Service Interruptions

Feb 28, 2024 | Kevin Lee

It’s all smooth sailing until the clear skies part and the storm rolls in, taking you away from the happy path. When your systems become more complex, the chance of unforeseen errors and service interruptions also grows, which could cause serious financial and reputational damage. 

It is not feasible to completely prevent such issues, but there are guidelines and tools that aim to deal with the sources of stress on your systems, and thus lower the chances of downtime. This is the topic of Part 3 of our Legacy Migration Series, which emphasizes how we can make our systems more resilient by using microservice design principles. Resilience here is not just about avoiding failures but about designing systems that can quickly adjust and recover from service disruptions.

Key Principles for Building Resilience

Resilience in payment systems is paramount, reducing interruptions, improving service reliability to customers and businesses alike. The migration process from legacy systems to microservices introduces challenges such as partial failures, version mismatches, and data inconsistencies, demanding a structured approach to bolster resilience.

Make the system fault tolerant. Implementing fault tolerance mechanisms like retries, fallbacks, and circuit breakers ensures the system’s robustness against failures, providing alternative paths or responses to maintain service continuity.

  • Retries: Automatic retries are implemented for transient errors that are likely to resolve on their own, such as temporary network failures. This mechanism attempts the same operation again, ensuring that momentary glitches do not result in failed operations.
  • Fallbacks: Fallback methods offer an alternative response when a primary service fails, ensuring that the system can still provide a useful albeit possibly degraded service. For instance, during real time payment processing, if a core banking system is offline, the traffic can be directed to a stand-in system that temporarily handles transaction processing.
  • Circuit Breakers: Inspired by electrical circuit breakers, this pattern prevents a cascade of failures by temporarily disabling a service operation if errors reach a certain threshold. This prevents resource starvation on calling services and reduces the effects of bottlenecks in the system.

Designing a system to be highly available means ensuring that the system is consistently operational, minimizing downtime to achieve near-continuous service.  Some methods to consider include load balancing, health checks and failover strategies.

  • Load Balancing: Distributes incoming traffic among multiple service instances based on observed utilization, ensuring no single instance becomes a bottleneck. Dynamic Load balancing that optimizes resource use and maximizes throughput works to improve overall system responsiveness.
  • Health Checks: Regular checks on service instances to assess their operational status. Unhealthy instances are automatically removed from the pool of available resources, ensuring that traffic is only directed to healthy, responsive services.
  • Failover Strategies: In the event of a service failure, failover mechanisms automatically redirect traffic from failed components to healthy ones, or to replicas in different data centers or regions. This ensures service continuity even in the face of significant infrastructure failures.
  • Self-healing: Use a combination of monitoring and orchestration tools to proactively detect, diagnose, and remedy faults without human intervention, enhancing the system’s reliability and availability.

Employing these resilience-building principles ensures that systems can withstand failures, maintain high availability, and automatically recover from disruptions, thereby safeguarding continuous and reliable payment processing flows.

How do Microservices Enhance Resilience?

Microservices architecture can enable key features that play a crucial role in achieving the aforementioned resilience principles:

  • Scalability and Flexibility: Microservices architecture allows you to independently scale services and make quick updates which contribute to the system’s flexibility, thereby improving its ability to recover from failures and handle increased traffic.
    • Dynamic Resource Allocation: In a microservices architecture, each service operates independently, allowing for the scaling of specific functions without the need to scale the entire application. This is particularly advantageous during peak usage times or when specific services experience increased demand.
    • Stress Mitigation: By allowing individual components to scale, microservices prevent any single point of failure from overwhelming the system. This distributed approach to handling demand ensures that traffic spikes or intensive processing requirements in one area don’t compromise the overall system integrity.
  • Rapid Error Identification and Isolation: Microservices architecture significantly enhances the ability to quickly identify, isolate errors and address them.
    • Service Segmentation: By dividing the application into smaller, loosely coupled services, issues can be contained within a single service. This segmentation means that a failure in one area doesn’t necessarily lead to a system-wide outage, as other services continue to function independently.
    • Advanced Monitoring and Observability: Tools and practices around monitoring and observability are integral to microservices. They provide granular insights into each service’s health and performance, enabling quick detection of anomalies or failures.
  • Minimized Deployment Risks: The microservices approach to deploying updates significantly reduces the risk associated with changes to the system.
    • Isolated Updates: Since each microservice can be deployed independently, updates or new features can be rolled out to specific services without risking the stability of the entire system. This isolation reduces the potential impact of bugs or errors introduced during updates.
    • Contract Testing: Ensures that the interactions between services remain consistent and reliable even as individual services are updated. This testing verifies that any changes to a service does not break its existing communication contract with other services.
    • Blue-Green Deployments: This deployment strategy involves running both the old and new versions of a service, gradually shifting traffic, and allowing for immediate rollback if needed. Microservice architectures enable this to be done at a service scope, saving on infrastructure costs. This, along with scalability, flexibility, and rapid error detection, enhances system resilience and the end user experience.

How can microservices address distributed system challenges?

Microservices, being distributed systems, rely heavily on network communication between services. While they may encounter temporary issues, there are methods, such as robust retry policies and failover strategies, to mitigate the impact of infrastructure glitches.

  • Automatic retries for transient issues: Microservices can have custom policies to retry failed requests without consequence. For instance, a failed request to fetch past transactions can be retried, while a payment interruption may need further review. With accurate error reporting, systems can become resilient to minor issues.
  • Flexible Failover Strategies for Critical Components: In system redundancy, there are various tiers of disaster recovery, with higher levels of redundancy costing more. Redundancy plans can prevent impact from a single malfunctioning blade in a datacenter to a natural disaster hitting a whole region. With microservices, individual services can have different redundancy tiers, with more focus on mission-critical systems. Backup infrastructure can be on standby or active for immediate failover, depending on the acceptable recovery time for a service.

These recovery mechanisms show that microservices have a natural ability to not only handle disruptions but to also prioritize the protection of critical systems while reducing cost. This adaptability in creating recovery strategies is crucial for preserving trust and reliability in critical systems, where availability and uninterrupted service are critical.

Closing Thoughts

Building resilience into your payment system architecture is a complex but crucial endeavor, pivotal in ensuring service reliability and continuity. Striving for five 9s (99.999%) availability by adopting a microservices architecture equips you with the tools and patterns necessary to significantly improve system resilience. The essence of resilience lies in anticipation, prevention, and rapid recovery from errors, safeguarding against extended downtimes and potential financial risks. Next, we will explore how to tackle unique security challenges during a migration in our 4th blog of the legacy migration series.  Thank you for reading and we invite you to follow Level19 for more great content!

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