KOCHI, India — As the sun set over Kochi’s historic Jew Town neighbourhood, Keith Hallegua donned a gray kippah and began a solitary walk to the synagogue at the end of his cobbled street.It was Shavuot, the Jewish holiday commemorating God giving the Torah to Moses. Hallegua reached the 458-year-old Paradesi Synagogue where he knew he would pray alone — without a minyan, the quorum of 10 males required for a communal service there. Hallegua is the synagogue’s last local congregant — the only Jew left in Jew Town. Across the city at the centuries-old Kadavumbagam Synagogue, Elias “Babu” Josephai...