SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f91ced24da8bf4fa84624709d8cafb306608215f47b35254e90fae3bc8f7844' 
  AND token = 'ET1TTPCwv4mFcAoLRs9hjV+CgXDCGKcFwv53xZxGqGk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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