SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39793132c901aca6c88f43ae422863244d49dae15816e99a9dde75c23b88cff0' 
  AND token = 'I9iZfJ2/qE3X/7sZ+F8vq/pmIu+a6E0kogtD4e5qAEY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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