SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81985335ab25bf65f2af66c42cd089a4386153d17e9387770a4b558e69789bfb' 
  AND token = 'xbTY8EmucXEFz43z5OPXVkgQvVqOki2Jo+sfiEMrbJs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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