When building genre-based artist discovery, Spotify genre tags include language/country prefixes (e.g., "french hip hop", "german rap", "turkish pop"). Without filtering, selecting "Rap" shows French, German, Turkish rappers mixed with US artists, which is confusing for users expecting English-speaking artists.

When running the app's Docker web container on a non-default port (e.g. 3003 instead of 3000), Spotify OAuth login fails with "Failed to authenticate". Three separate issues compound: 1) CORS blocks the OPTIONS preflight because the new origin isn't in FastAPI's allow_origins list, 2) The .env file overrides docker-compose defaults for SPOTIFY_REDIRECT_URI causing a redirect_uri mismatch during Spotify token exchange (frontend sends port 3003, backend sends port 3000), 3) Missing database columns (users.youtube_channel_id) cause a 500 error after successful token exchange because alembic migrations were incomplete.