SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b6ad96ef8808d53c7fcc52d8d927ff94315ebee3ac2849f99ea0c2d9b2d8b47' 
  AND token = '/K5Wun8apphXYPM9uv7HGP0tIgGkwEDSQm9b4sC/ZMU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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