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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f375f08e56ef19f947746e28dfe72f86007371f37b0da7a1ad37fedc6a4fcc3' 
  AND token = 'wktTAnM1JLn+h5b4teZiFdFVn/6uDRlh3+E/8nkndl4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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