SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7531bd9046bb874a656397f7d0c9f81f2a2c2eb59af04f767fbb4b447ff92b03' 
  AND token = 'U81nhYzY5nKZcpVUmV7YT+zqrVTGkm50WPXvliB1FHY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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