SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '928a2f87fb0e9d29352af6372be8e5011587513e871a9653f02528dd47541d36' 
  AND token = '87BUi6JjpPwdbiDUxB3Qc3ghiRxAHkb0DCd8Fda1KnM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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