SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50da3d58e3da92af7591e3a44eb793ef1dd542f811faec18942883f0e7b07100' 
  AND token = 'z6FZLkM/+p4APFDGVlghY5VFS0HHaUi/A4U8ZvwajjQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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