SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6c79372580af4178179c3e1b94be64a0a134f5b0b25b42310d78c5a831a7e9f' 
  AND token = '2MGdKPDoBDz4OtoBOJLpUwBCI+WMiOzKKrkCuHoxgmI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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