SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c3f14682518541ea30681932e3774a8794fd8a82eaf12e210f1ab5b682dbd1c' 
  AND token = 'ssVMjKlJUUXfDw+ehpXqDUkJBi/sWOM4k2d4gzycEWI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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