What's the best compliment you can give a piece of infrastructure? According to Maor Bril, who leads data infrastructure and several Labs products at Character.AI, it's that the product is boring.
Character.AI is one of the largest AI entertainment platforms in the world, with roughly 60 million monthly active users. To keep that experience safe and to constantly experiment with new prompts and models, the team needed to capture not just user messages, but the entire prompt sent to the LLM (system templates, character definitions, memory summaries, etc.) in near real time, at enormous scale.
They knew they wanted the Kafka API (their stack already spoke Spark, Trino, and ClickHouse). What they didn't want was the cost and operational pain of running Apache Kafka® in the cloud the old way. That search led them to WarpStream, and the rest of this episode of Confluent's Life Is But A Stream tells the story.
Interested in the full, technical case study of how Character.AI uses WarpStream? You can read it here.
"WarpStream is the most boring product I've ever got to work with. In infra, that's the biggest compliment you can ever give someone. It just works."
That theme echoes what we heard from Cursor in an earlier episode ("Data goes in, data goes out. It just works"). When you're a lean team, boring infrastructure is exactly what you want — it frees you to focus on the things that actually differentiate your product.
Maor had managed big Kafka clusters earlier in his career, so he knew the tradeoffs going in. WarpStream gave his team the Kafka ecosystem they already relied on, minus the parts nobody enjoys, like rebalancing partitions, adding brokers, and babysitting stateful clusters:
"It sounded too good to be true. It looks like Kafka, it talks like Kafka, but it doesn't have all the pain points of Kafka."
Because WarpStream Agents are stateless and run on Kubernetes behind an HPA, they simply scale up and down with the workload. And because everything is backed by S3-compatible object storage, durability and multi-region replication come for free.
When the team scoped out the numbers against the usual players, the gap wasn't subtle:
"It's a fraction of the cost of anyone else — about 10 to 15% total cost for a year. [That's an 85 to 90% cost reduction.]"
Normally, that kind of Kafka cost reduction usually means more DIY toil and more engineers to manage it. With WarpStream, Character.AI got the savings without giving up features or adding operational overhead.
A big reason is where the Agents run. As an AI lab leasing H100 nodes, Character.AI already pays for far more CPU than inference needs:
"Those CPUs are effectively free CPU compute that WarpStream Agents are running on. ... For us it was a win-win-win: cheap S3-compatible storage, our own BYOC compute we're already paying for, and all the data stays in our own project."
No third-party vendor in the data path, no new infrastructure to introduce, and in-cluster traffic means no surprise egress bills — even when you're moving a lot of data.
Because WarpStream is BYOC, the Agents run inside Character.AI's own VPC, and data governance got dramatically simpler:
"No user data ever leaves our own domain. That makes the whole story very easy to sell to our legal and security team. It was a win-win-win across the board."
The headline number isn't just cost. With WarpStream's Managed Data Pipelines (Bento running directly inside the WarpStream Agent), Character.AI built their processing pipelines in the same system that moves the data, and pushed it hard:
"We partnered with the WarpStream team on some custom connectors and built a bigger pipeline serving 5 gigs per second. And it just works."
That single pipeline now powers real-time trust and safety classifiers, prompt/model A/B testing, replay-on-failure debugging, trend analysis, and even ETL and reverse-ETL into a feature store (via a Bento connector the team contributed back to Bento).
One last reason WarpStream made it past the "too good to be true" filter: it's trivially easy to evaluate.
"With WarpStream, you can run it on your laptop in one command line. Functionally it works — that's awesome. Let's run this."
If you could prove out a streaming platform in a few minutes instead of a multi-week POC, why wouldn't you?
WarpStream is boring. And, as Character.AI will happily tell you, that's the highest compliment infrastructure can earn.
