SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eb429fb7bb749b40c530a644563523099b38c8da6206ae1bac47e019756dc8e9' 
  AND token = '0JS9mHiW4KGd+v8DAt0Vh2FfzVGObCq5IAiBg/Dg6bk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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