SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c63ba46d40d908290c6805c343473c37a76473ddc67f43063334c30dc0912f14' 
  AND token = '++OhPTsLg0ktInzwEshC7N22mtnG6AmiFnrj8RQbxck=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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