SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4a3a342a0fa73d8f6bf8245d7fbb795d9cb1617fdf9caee2b75d5c7b724cc5a0' 
  AND token = '/zBg/TpZKRV8UNjTwxOTnoeqAYrVdcNvDP5f+5itpQw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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