SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b9de343a615c388227c1f8fa4f1d5bd297be940a5d971c19db231a950a1d73e' 
  AND token = 'SS+b5qXJ/iEJC/zUFhNHOpE2v2BMUD7qd7xA9WXYJnw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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