SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'da3408972cb10cf0737a9518c329a07807b0261daaf50ae9a3d12dc33c04c197' 
  AND token = 'ot+cuzA4c5iwpoM8d+mGhbHndWTzEnwzYpbWnBlzuiw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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