AbstractMotivationNanopore sequencing is emerging as a key pillar in the genomic technology landscape but computational constraints limiting its scalability remain to be overcome. The translation of raw current signal data into DNA or RNA sequence reads, known as ‘basecalling’, is a major friction in any nanopore sequencing workflow. Here, we exploit the advantages of the recently developed signal data format ‘SLOW5’ to streamline and accelerate nanopore basecalling on high-performance computing (HPC) and cloud environments.ResultsSLOW5 permits highly efficient sequential data access, eliminating a potential analysis bottleneck. To take advantage of this, we introduceButtery-eel, an open-source wrapper for Oxford Nanopore’sGuppybasecaller that enables SLOW5 data access, resulting in performance improvements that are essential for scalable, affordable basecalling.Availability and implementationButtery-eel is available athttps://github.com/Psy-Fer/buttery-eel.