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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a851da80b50bd8be4f5c8c01a2077e1b7493ac34bd1648f8ee2257a3d259c306' 
  AND token = 'smqOXWGq3hnFE1QH3Bab+NNCI8vpB80MkXlcDjQQwPM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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