SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75a7b56a5c56585371dc543b33cdb31dc34413f5bf17014b9253a163fa831a83' 
  AND token = 'DxNqNmtCFTlHGEPgshHXBaGauGf+7uQ6NnLJjpTvKCU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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