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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8b4c647dcfd8f61cee22874dcd329d948b8bee517f02d7bafeeeb378fd12c0d2' 
  AND token = 'C3rrg9OYqUyaaRlJc2sOCKaXptgiDILCkYalUOVqZ+s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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