SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50b77e4e38f5167dbf83a322f5cfa9262a7635277401befbec9a422db38747a2' 
  AND token = 'NMHV2MMeGl3BOe+kFClfuG32fYT8WIoEwTbYAHnFH9A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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