Knowledge Units (KU)
What is a Knowledge Unit?
A Knowledge Unit (KU) is the fundamental economic unit of RushDB. It represents a unit of structured knowledge created and maintained by RushDB from your raw data — during ingestion, modeling, or reasoning.
Raw data → RushDB → Structured Knowledge → KU
The more data you push and the richer its structure, the more knowledge RushDB creates, and the more KU are consumed.
Developer Mental Model
You never need to think about nodes, edges, CPU, RAM, or storage. You simply think:
More data → more knowledge → more KU
RushDB handles all the underlying storage and graph mechanics automatically. You pay only for the knowledge created and maintained on your behalf.
What Generates KU?
KU is generated by operations that create or maintain structured knowledge in RushDB:
| Activity | Example |
|---|---|
| Ingesting records | db.records.create(), records.importJson() |
| Building relationships | db.records.attach() |
| Storing embeddings (number arrays) | Passing number[] arrays during ingestion |
| Compute-intensive operations | Vector similarity search, raw Cypher execution, multi-hop traversals |
| Maintaining stored knowledge | Ongoing footprint of stored records |
Standard reads and queries (find, filter, paginate) never consume KU. Compute-intensive operations do because their cost scales with dataset size rather than the data written — running a semantic search across 10M records costs significantly more server compute than fetching a record by ID.
Note: The internal weights assigned to each operation type are not exposed. You interact only with your total KU consumption.
KU and Plan Limits
Each plan includes a monthly KU allowance:
| Plan | Included KU / month |
|---|---|
| Free | 100,000 KU |
| Start | 250,000 KU |
| Pro | 1,000,000 KU |
| Scale | Usage-based |
| Enterprise | Custom / platform license |
When your workspace reaches its KU limit, write operations will be blocked until the next billing period or until you upgrade your plan.
How Nested JSON is Billed
When you ingest nested JSON, RushDB automatically decomposes it into separate linked records:
// Input: one nested object
{ "user": { "profile": { "name": "Alice", "age": 30 } } }
// RushDB creates:
// → Record: user (0 own properties)
// → Record: profile (2 properties: name, age) → ~2 KU
// → Relationship: user → profile → ~0.5 KU
// Total: ~2.5 KU
This means nesting does not multiply properties — it creates additional records and relationships, each billed independently.
| Component | Cost |
|---|---|
| Each record created | weight per record |
| Each property stored on a record | weight per property |
| Each relationship formed between records | fractional weight (< 1×) |
Note: Exact per-operation weights are not publicly exposed. You interact only with your total KU consumption.
KU Calculator
You can estimate your monthly KU consumption with this approximation:
estimated monthly KU
≈ records_per_day × 30 × (avg_properties + avg_child_records × relationship_weight)
Where:
records_per_day— average number of top-level records ingested per dayavg_properties— average number of scalar properties per recordavg_child_records— average number of nested objects per record (each becomes a separate linked child record)relationship_weight— the fractional KU cost per relationship (less than 1×)
For a quick estimate, nesting depth maps approximately to a combined multiplier of 1.0 (flat) → 3.0 (deeply nested) on the base property count. This is an approximation — actual KU depends on the internal weighting of each operation type.
Storage Footprint
RushDB charges a small daily storage footprint KU for every record currently stored in your project. This covers the ongoing infrastructure cost of keeping your data queryable.
- Storage KU is calculated once per day, prorated against your monthly plan allowance.
- The charge is proportional to your current record count — fewer records, lower footprint.
- Deleting records reduces your ongoing footprint from the next daily cycle onward.
- KU consumed at creation time is never reversed by a later deletion.
Self-Hosted
When running RushDB in self-hosted mode (RUSHDB_SELF_HOSTED=true), RushDB Cloud KU tracking is disabled and no cloud usage limits apply.