History of the Jews in Sofia
As per the 2021 Bulgarian census, the Jews in Sofia number around 901. Sofia had Jewish inhabitants before the ninth century; and in 811 the community was joined by coreligionists among the 30,000 prisoners whom the Bulgarian czar Krum brought with him on his return from an expedition against Thessaly, while a number of Jewish emigrants from the Byzantine Empire voluntarily settled in Sofia in 967.
Source: Wikipedia — History of the Jews in Sofia (CC BY-SA 4.0)