SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '99726b6fe3537f8da2e3e53b37df4a758bdf2587da74f2685336d8a950993a96' 
  AND token = 'u+mxlhOTpVJOUqKHwpd80jFft8FWDl/pnbpkQaULpI0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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