The increasing adoption of multi-cloud environments to mitigate risk and address geopolitical shifts was a central theme at QCon London 2025. In her talk, Teena Idnani, a Senior Solution Architect from Microsoft, guided attendees through the complexities of building resilient and consistent applications across multiple cloud providers. She used a compelling fictional case study of a traditional bank called FinBank, embarking on its multi-cloud journey.
Idnani highlighted the growing prevalence of multi-cloud, citing reports that 89% of organizations are leveraging it, with only a small fraction relying on a single cloud vendor. This trend is often coupled with hybrid cloud architectures, where organizations blend on-premise systems with various cloud services.
FinBank’s scenario illustrated this, with the bank strategically choosing to initially maintain its core banking on-premises while selectively migrating other components like risk management (to AWS for security) and advanced analytics (to Azure for AI capabilities). However, this distributed approach introduces significant technical challenges. Idnani delved into several key areas and offered practical mitigation strategies:
Addressing Latency Across Clouds
Latency becomes a critical concern when data and events traverse different cloud environments. Idnani emphasized the importance of reliable, low-latency connectivity options like Azure’s ExpressRoute and AWS’s Direct Connect. Beyond infrastructure, she stressed code-level optimizations such as using compression to reduce bandwidth and batch processing for efficient cross-cloud transfers. She also highlighted the importance of carefully adjusting timeout settings for retries and resource consumption.
Building Resilience in Distributed Applications
Resilience in a multi-cloud world extends beyond immediate availability to recovery after outages. Idnani advocated implementing event stores to persist events, enabling systematic replay capabilities to recover lost data. She also recommended leveraging resilience libraries like Kafka to manage transient and extended failures effectively. The importance of verifying delivery confirmations to ensure events persist successfully was also underscored.
Ensuring Event Ordering and Consistency
Maintaining the correct sequence of events across distributed components in different clouds is crucial, especially in transactional systems like FinBank. Idnani suggested publisher-side sequencing of events with strictly increasing sequence numbers. On the subscriber side, implementing checks to verify the order of processed events and employing deferred event processing for out-of-sequence arrivals are vital for data consistency. Event stores with quick update capabilities also play a key role in maintaining data integrity.
Handling Duplicate Events in a Multi-Cloud Setting
The risk of duplicate events increases when events cross network boundaries. Idnani recommended implementing defenses at both the publishing and processing stages, including using unique IDs for event identification and ensuring idempotency in processing logic to prevent unintended side effects from processing the same event multiple times.
Beyond these core technical challenges, Idnani touched upon other critical aspects of multi-cloud environments:
- Security and Compliance: The expanded attack surface necessitates a heightened focus on security and compliance across all cloud providers.
- Observability: Comprehensive logging, monitoring, and distributed tracing across different clouds are essential for maintaining visibility into the health and performance of distributed applications.
- Cloud Agnosticism vs. Cloud-Native: Organizations need to balance the benefits of cloud-native services with the desire for cloud-agnostic compatibility to avoid vendor lock-in.
Idnani concluded her talk with actionable recommendations for attendees:
- Standardize Event Handling: Consider adopting standardized cloud event schemas for consistent event management across different providers.
- Continuous Optimization: Regularly review and optimize architecture and implementation strategies to adapt to the evolving multi-cloud landscape.
- Invest in Team Skills: Emphasize team education and continuous upskilling to effectively handle the complexities of multi-cloud environments.
Idnani’s session provided a practical and insightful roadmap for navigating the challenges and harnessing the benefits of multi-cloud adoption. Through the lens of FinBank’s journey, she illuminated the critical considerations for building resilient and consistent distributed systems in an increasingly fragmented technological landscape.
