SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad8eb98a6c92259f38169dcd822888f297b3fb49f423b47dc69d7145d2c58652' 
  AND token = 'IuNQYNYm6NqvenJWvWS4YRHGkyvlXz9eEAbV5KHj6Vg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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