SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83453cba0429a6daeb063e974bc3530372a778cce5035e217aff251893aa0de8' 
  AND token = '3nMPfQpQr9k32ZUzhVsM5LwS52iZuOWutFtux1hXCg8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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