Firebase Realtime Database limits, all in one place
Most Realtime Database limits are the same on every plan; the one that scales with billing is simultaneous connections: 100 on the free Spark plan, 200,000 on Blaze. The rest — nesting depth, write rate, payload size — are fixed regardless of plan.
Last checked October 12, 2026.
Simultaneous connections
| Plan | Simultaneous connections per database |
|---|---|
| Spark (free) | 100 |
| Blaze (pay as you go) | 200,000 |
Sources: Firebase: Realtime Database limits
Fixed structural limits (every plan)
| Limit | Value |
|---|---|
| Maximum nesting depth | 32 levels |
| Key length | 768 bytes |
| String value size | 10 MB |
| Single REST write request | 256 MB |
| Single SDK write request | 16 MB |
Sources: Firebase: Realtime Database limits
Throughput and query ceilings
- Roughly 100,000 responses per second from a single database for broadcast and read operations.
- Writes: about 1,000 per second sustained, and roughly 64 MB per minute of write throughput.
- A query can scan at most 75 million nodes and must finish within 15 minutes.
- A write fans out to at most 1,000 Cloud Functions triggers (500 per region on 2nd-gen functions), each limited to a 1 MB event payload.
Sources: Firebase: Realtime Database limits
What actually bites in practice
The 32-level nesting limit is rarely hit on purpose but shows up fast in denormalized trees built by appending child objects without a plan; flattening deep trees into sibling paths keyed by id is the usual fix.
The connection limit on Spark (100) is the one that forces an upgrade decision earliest, since every open tab or reconnecting mobile client holds a connection until it is explicitly closed or times out.
Sources: Firebase: Realtime Database limits
Moving off Realtime Database
Scribase replaces a nested JSON tree with Postgres tables plus Realtime (subscribe to inserts, updates and deletes with an RLS-filtered query, not a whole-tree listener), so there is no 32-level nesting rule to design around and no fixed per-plan connection cap below the project's pooler limits. Each project is $25 a month.
Sources: Scribase pricing
Questions people ask
How many simultaneous connections does Firebase Realtime Database allow?
100 on the free Spark plan, 200,000 on Blaze. One connection is one open device, tab, or server app.
What is the maximum nesting depth in Realtime Database?
32 levels, on every plan. It is a structural limit, not a billing one.
Do Realtime Database limits differ between Spark and Blaze?
Only the connection count differs by plan. Structural limits (nesting, key length, payload size) and throughput ceilings are the same on both.