The LINE MANGA team, operating a popular digital comic service, faced challenges with their MySQL database architecture as their user base grew. They struggled to analyze reader behavior and optimize recommendations in real-time due to the complexity of joining data from multiple servers. To overcome this, they adopted ClickHouse, which allowed them to query MySQL directly without duplicating data or moving it into a separate system. This enabled real-time analysis, aggregation, and debugging capabilities, making their development process faster and more efficient. The team uses ClickHouse as a real-time query layer, leveraging its MergeTree table engine and condition pushdown feature to unify horizontally sharded data and aggregate sales in real time. By keeping things simple and using tools like clickhouse-local for local development, they've opened the door to real-time analytics without adding unnecessary complexity.