SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2e47070716c21c8c06169d926da203774fe88b165ff0ee2f6901470ca28c0544' 
  AND token = 'u78sMWasr+aoESDtX09XRHayHJqiaYhNF7heOxjdVIk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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