SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '791a33818c94854d1fc77751517d68203853d703883de314b06ca9552d7773a4' 
  AND token = 'uCaSgkswvkMQN+qZRBosXyTp1sFravrR+cnIFHxhO3k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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