SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2e8f31b4e6809bb3c13f610fd4cf500b7bfa3e422907d5e011ad5a6adbad3251' 
  AND token = 'MhhYmcsMgIpbRMVBkhhmk/zXXQjJfLBmSDXqj8wCJuQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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