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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a212b31e410633cd6c1125b5776d123b97f1e2c0147b664d155fe54ab6f7d41' 
  AND token = '3R57BjvMRHKN7BHByTrvzl8qlNri2PtoLL1ggQt2S8k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE								Impossible WHERE noticed after reading const tables