SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b338f802419f32e33cc050c9822f287ebf43fbfa78b7df327bfab861cf716788' 
  AND token = 'PVZOCZpBSdiQQThhMh08ACRv10M+2UV5dDaSkiZIt0Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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