Max pain for Fri's expiration is $230 (with some good margin vs $235) so there will downside pressure on Friday. Also - $238 is short-term technical resistance that it did not break through today solidly, so more reason for a decent drop on Friday. There could be trouble though if market good news works in by Fri that pushes overall market up, as next technical stop for AMZN is not until $247.50.
If AMZN starts down below $238 and no real good news in MKT, you can make money on a short Fri down to under $235 I woudl think. But if it breaks strong over $238 on good volume early, it could float up into low to mid $240's. So don;t short on temp weakness much above $238.