The document discusses lessons learned from building a real-time data processing platform using Spark and microservices. Key aspects include: - A microservices-inspired architecture was used with Spark Streaming jobs processing data in parallel and communicating via Kafka. - This modular approach allowed for independent development and deployment of new features without disrupting existing jobs. - While Spark provided batch and streaming capabilities, managing resources across jobs and achieving low latency proved challenging. - Alternative technologies like Kafka Streams and Confluent's Schema Registry were identified to improve resilience, schemas, and processing latency. - Overall the platform demonstrated strengths in modularity, A/B testing, and empowering data scientists, but faced challenges around