SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9d3ce3d5f5ef039788d8d04be47f5c68aabd693261e61a43e81b0e266416e58b' 
  AND token = 'MksurzsY5PpDUEyQXGdJU+Bh0LlNGlh2ajkUoJqqThU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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