SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fde3c763aa5bfd55506e5fcb80c3142cadce953e8db08e7f2290ffcd30415b6c' 
  AND token = 'VK4pxT8IDhLXC+U1j5ca1KvP/NdDVobuVH3DD+sl6RQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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