SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52981d884b078c33d1dd60bd0c5d3ca88b4b1c0172ec23d5ccf8c2a295f7a305' 
  AND token = 'gIU3aiohhYeheYX2YVIyAwWj9bdqIafAPXE/DLzYaKY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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