SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6890fb6e514d15cd34c23167ce2ca5a31e80f9982da37884fffba2bf1629ead1' 
  AND token = 'C/3c8SbrFnYsVm6b4owgQpH/cVJ6zFvEkMVGXJ/aP68=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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