Which Lightweight External Database Is Best for Permanent Log Storage in n8n?

Below is a brief explanation based on the available n8n documentation:

SQLite Usage in n8n

n8n uses SQLite by default to store credentials, workflows, past executions, and other internal data. This SQLite database is created as a local file (typically at ~/.n8n/database.sqlite) when you don’t provide another database configuration. However, it isn’t designed to act as an external, multi-user “log store” that you can easily query or integrate with other systems in the way that a dedicated database like PostgreSQL would be.

External Storage for Logs

If your goal is to permanently store custom log data that you can retrieve later, you might have two options:

1. Write Logs to a File or External Logging System

   • Use n8n’s built-in logging (or your own code) to write logs to a file on disk or push them to an external logging system (such as ELK, Grafana Loki, etc.). This keeps your workflow logs separate and doesn’t interfere with the internal database.

2. Use a Dedicated Database (e.g., PostgreSQL via the Postgres Node)

   • Although n8n supports PostgreSQL as an alternative for its internal operations, using it lets you connect external tools (like Supabase) to query your data. This approach is better suited to scenarios where you want a client–server database you can manage independently.
   • The video you mentioned likely showed using the Postgres node to store and retrieve data from a PostgreSQL database (such as via Supabase). This isn’t something that can be done with SQLite in the same way, since SQLite in n8n is meant for internal storage and isn’t accessed over the network as a service.

Redis or MongoDB?

• Redis: It is best used for caching or as a temporary store rather than serving as persistent storage for logs.
• MongoDB: Although not natively supported by n8n for its internal database, it might be used in custom workflows. However, setting up MongoDB solely to store logs can add unnecessary complexity if your needs are simple.

Recommendation

Given your requirement for a simple and permanent log storage that won’t interfere with n8n’s internal database:

• SQLite (external instance): n8n does not support running an external SQLite database (for example, connecting via a node to an external SQLite file) as a dedicated log store.
• PostgreSQL: While it might seem overkill, it’s the recommended option if you want a database that can be accessed externally. Using the Postgres node, you can write logs into a dedicated table in a PostgreSQL (or Supabase) database.
• File-based Logging: If you prefer simplicity, consider writing logs to a file or using a lightweight external logging service.

In summary, if you’re looking for an external, queryable database for log data, PostgreSQL (or a similar client–server database) is the path recommended by n8n’s documentation, whereas SQLite is intended for internal data storage and isn’t designed for that use case.