SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4200bb03dc2ae47694ccc8a365a614e99a8067aed4b3fd16e4a29b25457b51f3' 
  AND token = 'JStmC8UDgtUkNuHMp1qyG1z8CaY1DV8YLsiPV5lij+g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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