SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '903d3a7f828625c76fa51b78d51b43e082fbf3db406b927ddd238aefd5a6ba18' 
  AND token = 'au+bUCBz4RnfKZ/1YgXSYu8KMvzjvFhKFjpQAZhLJ4Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}