“…This tantalizing question was implicit in early works on deletion codes, particularly in [Ull67], which gave bounds on the achievable tradeoffs between rate and deletion fraction, and was explicitly raised in [KMTU11]. Since then, this question has been mentioned in several works, including the work of Bukh and Ma [BM14] which showed that an upper bound of 1 2 − 1 poly log N on the correctable deletion fraction, and many recent works on deletion code constructions such as [Wan15, GL16, GW17, BGH17, GL20, GHS20], other works on coding theory [ZBJ20], as well as the recent surveys [CR21,HS21]. In the other direction, the best known lower bound p thr del > √ 2 − 1 is due to [BGH17], who constructed explicit binary codes of non-vanishing rate to correct a fraction of deletions approaching √ 2 − 1 (see [SZ99,KMTU11] for prior constructions).…”