The actual problem seems to be the lowzoom_lakelabel view, it works when only requesting one row, but with two rows it already runs for several hours without coming to an end:
gis=> \timing
Timing is on.
gis=> SELECT * FROM lowzoom_lakelabel limit 1;
way | name | label | way_area
--------------------------------------------------------------------------------------------+------+----------+-------------
0102000020110F00000200000072C42F42A7A9444106EBC942CFDE5541B001E775EBAA444106EBC942CFDE5541 | Olt | lakeaxis | 2.22856e+06
(1 row)
Time: 33.325 ms
gis=> SELECT * FROM lowzoom_lakelabel limit 2;
[... I gave up waiting after ~8 hours ...]
The actual problem seems to be the lowzoom_lakelabel view, it works when only requesting one row, but with two rows it already runs for several hours without coming to an end: