Given a chance …
That pass from East is interesting. That means he has equal length in minors – so 1-1,2-2 or 3-3.
How about West’s 3♦ ? Does he have 6-5? Probably, though could be 5♦ and 5 bad ♣ .
If 3-3 pd has ♣ void, 3♦ and so 10 major cards. In this case 4M should be on for you. If 1-1, pd has 2♣ ,5 ♦ and would happily convert 3♦ dbl. But most likely RHO has 2-2. In this case partner has 1♣ and 4♦ . Given RHO electing to bid diamonds over clubs, partner with very little values and 4 poor diamonds won’t be able to convert. Still that gives him 8 major cards, and if they are 5-3 or better, you should have a play for 4M. Only if he has 4-4, you may be in a bad spot. Anyway, you choose to double and partner bids 3♠ . What now?
Partner’s choice of 3♠ is interesting. With 4-4 you’d expect him to bid 3♥ , so he should have 5♠ . Do you raise?
If partner expects you to make one more move, he may bid 3♠ with 4-4, intending to bid 4♥ next time round. In that case 3♠ could easily be your limit. But perhaps partner can give you something like ♦ T9xx – a second stopper. In that case you might have play for 3NT.
You elect to bid 3N, partner bids 4♥ confirming your worst fears and you put him back to 4♠ hoping that partner is 5-4 and RHO 6-5 in minors.
Move over to partner’s seat to play the hand
If West is 2-1-5-5, it does not matter who has the CK, when he returns a D to the King on the table. You can cross to the SQ, and run the C9. If East has the King, the club winners can be rammed through him as trump substitutes. If the C9 wins, you have 6 winners outside trumps, and they cannot prevent you from ruffing the 4th H on the table with the 10, and score your little trump en passant — after C9 wins, cross to cash H winners, CA, and play C ruff over ruff, ruff H, club again so that their trump and D tricks clash.