SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f6f1a1011744e92ea5d21c51f48562ce196a9220b2984f813dde145fee6bda2' 
  AND token = 'QEcuMRf7P8V3pZnp/BIykjnNdiN2GajBG/f8S8/wRGE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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