# Troubleshooting

> Symptom-led diagnosis for a NYXDB node, with the system relation that explains each symptom.

| Symptom | Where to look |
| --- | --- |
| Writes slow down | `pressure_stalled` and `accepting` in `system.tablets`; `rejected_mutations` in `system.storage`. |
| WAL keeps growing | `system.wal_reclamation_blockers`. |
| A derived table lags | `system.transformation_revisions` and `system.derived_lineage`. |
| A stream falls behind | `system.psi_streams`: demand, queued frames and lag per subscription. |
| A query runs long | `system.queries` and `system.query_stats`. |
| A federation source is not ready | `system.sources`. |

See [System relations](/docs/operations/system-tables).

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Source: https://nyxdb.io/docs/operations/troubleshooting/