SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '38b837e799e4b66a5bf033deb459f47904adf23bad85ec74e84419bef719ea52' 
  AND token = 'pLGxWNbbnSuSONkuoQFey1K9boJoffUUw+fNRihjkTw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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