SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '751f12f4e41891a00b103f95fd1f7b9407663a4cdfec231b07b648e3042c01e3' 
  AND token = '+h1FKTEjrO/OqJlTiTpZkHbquFzFGEvHvk5tSaTy/zI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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