SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a8847189051fe1b6e3c0768e9948506c615292d73fd2b6d07d1cc1b8fe5d5d2' 
  AND token = '2MVQQnZpklJgOOd3vgmFuzwW/z4p56rUPNPK53bQjNw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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