Change automatically derived citekey in biblatex with alphabetic style

Question

I would like to change the automatically generated citation key of biblatex when using the style alphabetic. So far I only know the possibility via the field shorthand. But I would like to have the citekey automatically derived from the last name of the author and the year. If there are two authors it should be Last Name 1 and Last Name 2 and the year. If there are more than two authors it should be Last Name 1 et al. and the year. Is there e.g. the possibility to address the year and last name within a bibitem (e.g. `bibauthorlastname`) and do something like

@article{articleA,
title={This is a long title of article A},
author={Albert Einstein},
journal={Some scienece journal},
volume={1},
number={4},
pages={42--125},
year=1950,
publisher={Hellsevier}, 
shorthand = {\bibauthorlastname \bibyear}
}

Or do I have to approach the matter in a completely different way?

Here is a MWE, where the citekey entry is formatted as it should be (but not automatically).

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}
\usepackage{lmodern}
\usepackage{filecontents}
\usepackage[                        
    backend=biber,                  
    bibencoding=utf8,               
    style=alphabetic        
]{biblatex}

\begin{filecontents*}{\jobname.bib}
@article{articleA,
title={This is a long title of article A},
author={Albert Einstein},
journal={Some scienece journal},
volume={1},
number={4},
pages={42--125},
year=1950,
publisher={Hellsevier}, 
shorthand = {Einstein 1950}
}

@article{articleB,
title={This is a long title of article B},
author={Ludwig Boltzmann and Erwin Schrödinger},
journal={Another science journal},
volume={42},
number={1},
pages={43--49},
year=1970,
publisher={Hellsevier},
shorthand = {Boltzmann and Schrödinger 1970}
}

@article{articleC,
title={This is a long title of article C},
author={Ludwig Boltzmann and Erwin Schrödinger and Werner Heisenberg},
journal={Another science journal},
volume={4},
number={1},
pages={10--50},
year=1980,
publisher={Hellsevier}, 
shorthand = {Boltzmann et al. 1980}
}
\end{filecontents*}

\addbibresource{\jobname.bib}

\begin{document}
This is a test for citation \cite{articleA}. And here is another test \cite{articleB} and also \cite{articleC}.
\printbibliography
\end{document}

Answer 1

The style you describe is an author-year style, so it seems more straigtforward to base it on style=authoryear rather than style=alphabetic.

If you want to retain the square brackets around citations and the repetition of the citation label in the bibliography, I suggest you have a look at biblatex-ext's ext-authoryear style. Its citation delimiter feature makes it easy to obtain square brackets instead of the usual round brackets (with \DeclareOuterCiteDelims), its introcite option makes it easy to repeat the citation label in the bibliography.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[ngerman]{babel}
\usepackage{csquotes}

\usepackage[
  backend=biber,
  style=ext-authoryear,
  maxcitenames=2, mincitenames=1,
  uniquelist=false,
  maxbibnames=999,
  introcite=label,
]{biblatex}

\DefineBibliographyStrings{german}{
  andothers = {et\addabbrvspace al\adddot},
}

\DeclareOuterCiteDelims{parencite}{\bibopenbracket}{\bibclosebracket}
\DeclareFieldFormat{bbx@introcite}{\mkbibbrackets{#1}}

\begin{filecontents*}{\jobname.bib}
@article{articleA,
  title     = {This is a long title of article A},
  author    = {Albert Einstein},
  journal   = {Some Science Journal},
  volume    = {1},
  number    = {4},
  pages     = {42--125},
  year      = 1950,
}
@article{articleB,
  title   = {This is a long title of article B},
  author  = {Ludwig Boltzmann and Erwin Schrödinger},
  journal = {Another Science Journal},
  volume  = {42},
  number  = {1},
  pages   = {43--49},
  year    = 1970,
}
@article{articleC,
  title   = {This is a long title of article C},
  author  = {Ludwig Boltzmann and Erwin Schrödinger and Werner Heisenberg},
  journal = {Another Science Journal},
  volume  = {4},
  number  = {1},
  pages   = {10--50},
  year    = 1980,
}
\end{filecontents*}
\addbibresource{\jobname.bib}

\begin{document}
This is a test for citation \autocite{articleA}.
And here is another test \autocite{articleB}
and also \autocite{articleC}.

\printbibliography
\end{document}