i am trying to make a little express app wich returns data from a postgres query.
the query result should be chaced in a redis db. what i do is this:

app.get('/query_tile/:z/:x/:y', async (req: Request, res: Response) => {
    const client = new Client(connection);
    await client.connect();
    const setHeader = () => {
        res.set('Content-Encoding', 'br');
        res.set('Content-Type', 'application/x-protobuf');
        res.set('Vary', 'Origin, Access-Control-Request-Method, Access-Control-Request-Headers');
        res.set('Content-Disposition', `attachment; filename=tile_${z}_${x}_${y}.mvt`);
    }
    const { z, x, y } = req.params;
    const cacheKey = `tile_${z}_${x}_${y}`;
    const cachedData = await redis.get(cacheKey);

    if (cachedData) {
        
        setHeader()
        res.send(brotliCompressSync(cachedData));

    } else {

        const { rows } = await client.query('SELECT query_tile($1, $2, $3)', [z, x, y]);
        const data = rows[0];
        const compressedData = brotliCompressSync(data.query_tile);
        await redis.set(cacheKey, data.query_tile);
                
        setHeader()
        res.send(compressedData);
    }
    client.end()
});

the issue i am having is, that the cached result is not the same as the not cached one.
what am i missing here?

both returns do have some data in it, but the one from the cache is not readable. at least not how i need it.

Thanks a lot for help!