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svlachakis merged 1 commit into from
Sep 11, 2026
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docs: JSON-RPC response streaming for traces and logs #362

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18 changes: 18 additions & 0 deletions docs/interacting/json-rpc-server.md
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## Streaming responses

Some methods can return a response far larger than the request that asked for it: a block trace, or a log query over a wide range. Nethermind writes those responses to the transport as it produces them, instead of building the whole response in memory first. The memory a request costs is then bounded by the stream rather than by the size of its result, and the first bytes reach the caller before the node has finished the work.

### Traces

[`JsonRpc.EnableTracingStreamMode`](../fundamentals/configuration.md#jsonrpc-enabletracingstreammode) streams the `debug_trace*` and `trace_*` responses as the transaction executes. It is enabled by default. A `debug_trace*` call can override it for that request with the `streamMode` option, for example:

```bash
cast rpc --rpc-url http://localhost:8545 debug_traceBlockByNumber latest '{"tracer":"callTracer","streamMode":false}'
```

Streaming bounds the memory of a trace and lowers the time to the first byte. It does not change how long the trace takes to produce, since tracing re-executes the block.

### Logs

[`JsonRpc.EnableLogsStreamMode`](../fundamentals/configuration.md#jsonrpc-enablelogsstreammode) streams the `eth_getLogs` and `eth_getFilterLogs` responses as matching logs are found. It is disabled by default, because it changes what a caller receives when a query is too large: instead of buffering the whole result and returning a limit error, a streamed response stops at [`JsonRpc.MaxLogsPerResponse`](../fundamentals/configuration.md#jsonrpc-maxlogsperresponse) or [`JsonRpc.MaxLogsResponseBodySize`](../fundamentals/configuration.md#jsonrpc-maxlogsresponsebodysize) and ends there. Authenticated requests are not subject to those limits.

The exhaustive list of supported JSON-RPC methods can be found under the JSON-RPC namespaces.