SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fc2de89d5dc13cdb9ddcf2eadb3dd9ac05cf0b8a278e8b048b3698708cd841b' 
  AND token = '3rQSvN6ZLec49dLC3U970hbD9IqiGlbuOOpOx4pnXH4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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