WIP: Dockerfile that might be able to build Nix dependencies first in a separate layer. Ref: https://mitchellh.com/writing/nix-with-dockerfiles#user-content-fnref-2

Dockerfile

FROM nixos/nix:latest AS builder

RUN nix-env --install jq

COPY . /tmp/build
WORKDIR /tmp/build

RUN drvpath=$(nix --extra-experimental-features "nix-command flakes" derivation show | jq -r 'to_entries[0] | .key') \
    && echo $drvpath is the path \
    && closure=$(nix-store --query --requisites $drvpath | grep -v -F $drvpath) \
    && nix-store -r $closure
RUN nix \
    --extra-experimental-features "nix-command flakes" \
    --option filter-syscalls false \
    build

RUN mkdir /tmp/nix-store-closure
RUN cp -R $(nix-store -qR result/) /tmp/nix-store-closure

FROM scratch

WORKDIR /app

COPY --from=builder /tmp/nix-store-closure /nix/store
COPY --from=builder /tmp/build/result /app
CMD ["/app/bin/app"]