SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c28747088359ce4f6d33b8128d48b2cc38935e22ebc75cb545f101c594aa0c68' 
  AND token = 'kgB0UP9hxZh5iyVunFVADLCztqUxkORughkGQtweZuU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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