SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c7e4ab57500bf09b24919f12ef6f7e2931bb40aae621d63f0bd3f458f19829' 
  AND token = 'FsYiLMDpc0hV15orHKnXubddU+zQ/PPkYLbEdEgOSDI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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