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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f28bdc3376d4756180937955ef36d6ef3639f2af32742d36d86e258b1e1c6840' 
  AND token = 'tibkI/6SCJso6KcY/SWMAdzzy13PYOtoae9fOn+3zLA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}