SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '03963f1636c5f4464d7e835647f6eea71b388f8bcf0589638e4d15ff5cea74b2' 
  AND token = 'brgZiWH+clpGhdYFQwvutnXKJ7qRGOLbnsJ+mWIZhcQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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