Very loosely adapted from Vivek Singh.
The marinade is a quick marinade, so I recommend focusing first on the marinade, and then letting the shrimp marinate while you prep everything else.
Whisk together all of the marinade ingredients except the shrimp. Place the shrimp in a large, sealable plastic bag and then add the marinade. Gently massage the marinade into the shrimp, and then seal the bag and place it in the fridge.
Make sure all of your stir fry ingredients are prepped before you begin (onions are chopped, curry leaves counted, etc).
Place the vegetable oil and mustard seeds in a large, somewhat deep frying pan (a wok works obviously, as does a nonstick pan or a large cast iron pan; in India they would probably use a kadai). Turn the heat to high or medium high if high is too hot for the pan you are using (like nonstick). Partially cover the pan to allow the mustard seeds to pop without escaping the pan.
When the mustard seed popping slows, remove the lid and carefully add the curry leaves--stand back because they will splatter!
As soon as the splattering slows a bit, add the chopped onions with a pinch of salt. Begin stirring and moving the onions around the pan.
Keep stirring for 5 minutes on high heat, maybe closer to 10 on medium high. You want some good color on the onions.
Add the garlic, ginger and chile pepper with another pinch of salt. Stir for another 2 minutes.
Add the tindora with a pinch of salt. We loved the tindora tender but still crisp; stir fry for 3-5 minutes, depending on how thinly you sliced your tindora. Taste one before adding the shrimp--it should still be quite crisp but no longer taste raw.
Add the shrimp with any accumulated marinade. Toss and cook quickly--as soon as the shrimp curls closed and becomes opaque pink, they are cooked through. It will probably take 3 minutes or less, so be careful to not let them overcook and dry out.
Taste for more salt and then serve immediately with Basmati rice and wedges of lime or lemon.