SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76210bc391eaf21e971ae27516ecd6801f9c858ba76ebd07a5e24dd97896e60e' 
  AND token = 'PuG4nBvfKgzFMkys0wNkgscYxwZBLXTLY+aKLDgGZIE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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