ScyllaDB cut Sprig's read latency 4X after Redis and ClickHouse hit a wall

Justy So Sprig's fintech platform was humming along until their read latency started tanking. Redis and ClickHouse just couldn't keep up.

Cody Yeah, and that's the story nobody likes to hear—you pick the tools everyone says are solid, scale them the right way, and then hit a wall that's not about how hard you're trying, it's about what those databases actually do well. Sprig's read traffic was outpacing what either of those tools could handle cleanly.

Justy What do you mean by that? Like, isn't Redis basically just—fast?

Cody Redis is fast for what it does, but it's in-memory and single-threaded at its core. You can shard it, sure, but you're still fighting contention under really heavy concurrent read load. And ClickHouse is built for OLAP—analytical queries where you're scanning millions of rows and you don't care about latency on individual requests. Sprig needed something that could handle millions of individual reads per second with sub-millisecond response times. Different beast entirely.

Justy So they landed on ScyllaDB. What's the actual pitch there—just another NoSQL thing, or?

Cody ScyllaDB is Cassandra, basically, but rewritten in C++ instead of Java. That matters more than it sounds—no garbage collector, no JVM pauses, and the whole thing is tuned for throughput and latency under load. It's wire-compatible with Cassandra, so if you know that API, you're home. But what made Sprig's case work is that they had a read-heavy, time-series-ish workload that maps cleanly onto Cassandra's data model.

Justy And they got 4x latency cut from that swap.

Cody Right, which sounds like marketing until you think about what that actually means for a fintech app—the difference between 100 milliseconds and 25 milliseconds on a user-facing read is massive. One feels snappy, one feels broken. [pause] But here's the thing, Justy: this only works if your schema fits. Cassandra isn't a relational database. You can't do complex joins. You design around partition keys, and if you get that wrong, the whole thing falls apart.

Justy So this is a 'if you know what you're doing' move, not a general upgrade.

Cody Exactly. You need a workload that's write-heavy or read-heavy but not both in weird ways, you need to be comfortable with eventual consistency instead of ACID, and you need the operational chops to run a distributed system. Sprig probably had that. Most teams don't start there.

Justy Who actually uses this in the wild? Like, what's the market story here?

Cody Time-series databases, analytics platforms, high-frequency trading, recommendation engines—places where you're grinding through billions of events and you need predictable latency. There's also a managed version now, so you don't have to run the cluster yourself. That lowers the barrier a bit.

Justy Okay, so adoption barrier is still pretty high—you need to know Cassandra or be willing to learn it, your schema has to fit, and you're betting on a smaller ecosystem than Postgres or even MongoDB.

Cody Yeah, and there's risk in that. Sprig has the team and the scale to justify it. A startup with five engineers and a Postgres database? They should not be thinking about ScyllaDB. But if you're shipping millions of reads a second and your current database is melting, it's worth looking at. [chuckles] And honestly, the fact that it's Cassandra-compatible is huge—it's not like learning a brand-new thing from scratch.

Justy So if someone wanted to kick the tires on this, what would they actually do?

Cody Start with their Docker image or spin up a managed cluster on their cloud offering. Design a schema for whatever your hot read pattern is—like, if you're tracking user events by timestamp and user ID, make that your partition key. Then load some real data and benchmark it against what you're using now. Don't assume the latency gains until you've measured them with your actual queries.

Justy And for someone just tinkering alone?

Cody Set up a local cluster with Docker, grab a time-series dataset—stock prices, sensor readings, whatever—and load it in. Run a bunch of concurrent reads against it and measure the latency. Then do the same thing with Postgres or Redis on the same hardware and see where you actually stand. That'll tell you whether ScyllaDB is even relevant to what you're building.

Justy Right. So it's not magic, it's just really good at a specific job.

Cody Exactly. And knowing when that job is yours is the hard part.

Justy Well, Cody, if you're dealing with a read latency wall and general-purpose tools aren't cutting it, ScyllaDB's worth a look—just make sure your schema actually fits before you commit.