SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51c5dd3959378a0cd397acda1e5f07a396af89165eaa1e19992b07cbdd0d075d' 
  AND token = 'raDYyGvgHspEDswpubk4sRocU6SE3pj8ZoIMmws7Plc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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