RisingWave vs ksqlDB: Which SQL Streaming Engine Should You Choose?
RisingWave is a PostgreSQL-compatible streaming database with open-source Apache 2.0 licensing. ksqlDB is Confluent's SQL engine for Kafka with Confluent Community License restrictions. Choose RisingWave for PostgreSQL compatibility, non-Kafka data sources, and open-source flexibility. Choose ksqlDB if you're fully committed to Confluent Cloud and need the tightest Kafka integration.
Key Differences
| Feature | RisingWave | ksqlDB |
| SQL dialect | PostgreSQL | KSQL (non-standard) |
| Connect with | psql, any PG driver | ksqlDB CLI, REST API |
| Data sources | Kafka, CDC (PG/MySQL), Kinesis, S3 | Kafka only |
| Data shuffling | Automatic | Manual repartition required |
| State storage | S3 (managed) | RocksDB + Kafka changelog |
| Max queries | Unlimited | 40 per cluster (Cloud) |
| UDFs | Python, Java, Rust | Java (not on Cloud) |
| License | Apache 2.0 | Confluent Community |
| Iceberg sink | ✅ | ❌ |
| Self-hosting | ✅ | ✅ (with restrictions) |
The Kafka Lock-In Problem
ksqlDB requires all data to flow through Kafka. Need data from PostgreSQL? First set up Kafka Connect + Debezium to get it into Kafka. RisingWave ingests directly from PostgreSQL/MySQL CDC — no middleware.
Frequently Asked Questions
Is ksqlDB open source?
ksqlDB uses the Confluent Community License, which restricts offering it as a competing SaaS. It is not a true open-source license. RisingWave uses Apache 2.0 with no restrictions.
Can RisingWave replace ksqlDB?
For most use cases, yes. RisingWave processes Kafka streams with standard PostgreSQL SQL, supports complex joins without manual repartitioning, and has no query limits. The main ksqlDB advantage is deep Confluent Cloud integration.
