SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8a31c3ef320268eb0422d6e12f298a88a2921837bec34f08e1228d9ba8070f7' 
  AND token = 'a3QrFyLV2B3IeVBVn6mQYczRPSpNRUj4apdDGQUzEtI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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