SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ef66628855f0f607690cfae47bb4f7e7fe1016c1bc9738256269ff63e04d317' 
  AND token = 'mFcR88r71CoOA+bUMK9ezyfmXqCVSWQnv4U82ViIxEI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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