sending data from redis (as cache) does not return the same data

i am trying to make a little express app which returns data from a postgres query.the query result should be cached 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!