SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '54b6eb47b6c042491103a417285f7cd285a16315732436e488a95936d43459a6' 
  AND token = 'xfTSCEmFELZjlqOrVqHGquMDlD+IURhjFPNgGvdsy2w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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