This question What objects can & can't penetrate ground based shield generators? has an answer that established Star Wars energy shields to date to be kinetic - nothing can pass through it above a threshold speed. Starkiller Base, however, uses shields that has a refresh rate, oscillating between active and inactive states at a given rate.
In Star Wars, hyperspace travel is essentially normal space travel at FTL speeds. Given these facts, a few points need clarification:
- Does Starkiller Base use the same shield technology as those used by kinetic shields during the Clone Wars & the Galactic Civil War?
- If no, is this considered a post-Empire technological advancement, and is it a known technology to the wider galaxy?
- If yes, then why is there both an upper and lower speed threshold to the world technology without contradicting each other?
- Also, if yes,
why can't you just sneak Ham & company onto the planet (the Resistance managed to sneak ships to the system to gather intelligence) and walk through the shields on foot rather than do what they did, the odds of survival are so remote? The only other person I've seen in canon jump with such proximity and precision is Anakin, a Jedi.