SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3791be833d6ac840b8c06d83862d73e148f2166562e1268ebace8b546b99d658' 
  AND token = 'V4GTvjARoUnCARhrOzOe4OhrcnNYZAyZ6R5LUpfOq5k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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