SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68828d7815744472162fdf8ade43ad10fbe6b11d7cf6ada08022829013598281' 
  AND token = 'jxE29pCSBErRus79rtUJBDjhRHW4lD2TqW9LnCGnYwo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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