SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '502f4e65aa38d03aae53c9040180ad7de9d034c60a8b18a8419856186229387d' 
  AND token = '0P/gPnirgu6pddO5RVR1mDIOAiBkE+x/IO+YXyxMSMM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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