SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e687ac91a781bcfbfbe7e38f48e91aaed2e47c25546954ab9ca04705775db743' 
  AND token = 'Tj0FYu3oXrkjKpqVYZt9/93LHhzPuQRQtoZDZh6IRZc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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