SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9aaa2ecb2f3b6911cb1c8711be74f965faf26c5f978e74704ff0f68e09f39ba' 
  AND token = '7XViFd/fiee0eiFTVsl+jRKFBMQwkzZ5GqxkdGY/D/Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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