SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c47dd369fecda287672fca608259ead80902df7812f3c6d41a50df5459938d41' 
  AND token = '9Vuqic2637SmcHZdz8DAjxZQnE3hPF0WEqvcWjLwzbQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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