SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd50b571def90af9ddcacce5940b0179f11840b295401342186a042da99a8cff5' 
  AND token = 'zO3Nz6/Ac32n+agub3NC/mBPQ+OwsJdh+SLt58RpKGw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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