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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e81e00b698b807e1feba28d2462e3ae1de2384c9dcfb7c70ce1b10e74d594a03' 
  AND token = '8KhcO27ob+Rxw7UCB8fknqj/ahwoiEtgEbzExmXzZ84=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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