SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef8896d21826ef6bdf0eca95de474526b8539cfdc7895795df65665f6a855488' 
  AND token = 'COfBUIGf6AmW9peVVyBjDWOzb1WoB+J6/XCt0YXXe4g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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