SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6ed347476420962727155589796db646bdadbbdd423f8c3e4af4ff2379c9891' 
  AND token = '7t1w2ZKhTgPLdFlXVPfLlyqYiwtsSwgqkxO+VQhgvXM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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