# Frequently Asked Questions


  **Question: How do I properly use PostgreSQL in HA mode?**

In High Availability (HA) mode, PostgreSQL runs on multiple containers with a primary node and replicas. To get the most out of this setup:

    - Use port `5432` for all write operations (INSERT, UPDATE, DELETE) — this always routes to the primary node
    - Use port `5433` for read operations (SELECT) — this distributes queries across all replicas, improving performance

    The read replica port (`5433`) is only available in HA mode. If you're running PostgreSQL in single container (NON_HA) mode, only port `5432` is available.

    See [Connection Parameters](/postgresql/how-to/connect#connection-parameters) for all available ports and environment variables.

  **Question: Why is my connection to PostgreSQL from third-party software failing?**

*One possible cause:* 

    The connection string in Zerops always starts with `postgresql://`. While the official PostgreSQL documentation
    states that both `postgresql://` and `postgres://` URIs are valid, some software requires the shorter `postgres://`
    version.
    
    To resolve this, create your own environment variable with the correct URI. For example, if your PostgreSQL service is named `db`, use the following format:
    
    ```
    postgres://:@:
    ```