SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '356ebf4d4c7d5192303f003af82898581f3d1cb9e03f73845980e130a499235e' 
  AND token = 'EjiYlbhzJBvGNdOMOLU6Qms2UMvACDkP8bKeDGaJWNw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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