SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ceff3af10a1fb7c0690515e9613b5bb593561f6432c314a21cede1e8e433e47' 
  AND token = 'kxZ4ES0UCJnGfRjl+PoXviXFj9XTxfyrcW2ChBbenvE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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