This is something we mention in the third section of the article: dead tuples and autovacuum caused real performance hits, which we (partially) mitigated through index optimization (minimizing the number and size of indexes, and making indexes partial).

PgQue is a really interesting system! However, its semantics are quite a bit more similar to Kafka than to a job queue, which is good for some workloads and not for others. For example a truncation-based deletion system is fast but inflexible, and not suitable for a job queue system because a single long-running job (and DBOS supports workflows that run for months) can block truncation.