SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76323a845e421058ceff255eb34d8c34bcf5d36eeb8b02c184493ffa1ad19fb7' 
  AND token = 'DsQbdoQJO/PocOEvAqmdHC0UT4QUXP1pAdz7HHTXGLI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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