SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '521197a741890815a4c719beca186f0a06689ecbd24fe850a6e993a811aed5dd' 
  AND token = 'XMj044CMl+KM8bY0os/gZliFiYCaLxNyBrh+5N/VuME=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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