The best replacement for fers is csrs.

The best alternatives to fers are rated as following:
★★★★★  csrs
★★  tsp
★★  csrs retirement
★★  cers
★  crs
★  crcs
★  pers
★  csrs offset
★  calpers
  fers rae
  csrs better
  military retirement
  civil service retirement system
  fsps
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  civil service
  csrs which is better
  owcp

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Speaking about fers, one probably shouldn't forget about military retirement.

Other search terms related to fers and their ratings are:
★★★★★ military retirement
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