SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a8521b0de646bc4c48005ef6eca364010b8daf0e1e18a45fe574fa35666e73c' 
  AND token = '3pT2sKZpBpD79y2jxCKlbXHLC4zmQUVCz6ftODJZ8q4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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