question about the slow MySQL SELECT query with a WHERE clause on an indexed column:

You might want to check a few things that could be affecting query performance:

1. *Index Usage*: According to you, `EXPLAIN` shows the query is using the index. Yet performance is still poor.

2. *Data Distribution*: If the data distribution in the indexed column is uneven, the MySQL optimizer might make suboptimal decisions.

3. *Query Structure*: You could try optimizing the query structure. Maybe there's a way to optimize the `WHERE` clause.

4. *Table Size and Row Count*: 2 million rows is a moderate size, but if the row size is large, it could affect performance.

You could suggest:

- Check if the MySQL optimizer is choosing the correct index.

- Try using a `FORCE INDEX` hint to see if performance changes.

- Use query optimization techniques like using a covering index.

- If the problem persists, check MySQL server configuration (like `innodb_buffer_pool_size`).