  The extension of interpolation-grid frameworks for perturbative QCD
calculations at next-to-next-to-leading order (NNLO) is presented for deep
inelastic scattering (DIS) processes. A fast and flexible evaluation of
higher-order predictions for any a posteriori choice of parton distribution
functions (PDFs) or value of the strong coupling constant is essential in
iterative fitting procedures to extract PDFs and Standard Model parameters as
well as for a detailed study of the scale dependence. The APPLfast project,
described here, provides a generic interface between the parton-level Monte
Carlo program NNLOJET and both the APPLgrid and fastNLO libraries for the
production of interpolation grids at NNLO accuracy. Details of the interface
for DIS processes are presented together with the required interpolation grids
at NNLO, which are made available. They cover numerous inclusive jet
measurements by the H1 and ZEUS experiments at HERA. An extraction of the
strong coupling constant is performed as an application of the use of such
grids and a best-fit value of $\alpha_s(M_Z) =
0.1178\,(15)_\text{exp}\,(21)_\text{th}$ is obtained using the HERA inclusive
jet cross section data.
