SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21a4afe6fb405c7a94478b681d0da0223d2b631ec09f4dfeff056afa624e1e9c' 
  AND token = 'v7I4DmudppXYi4YpbqasWcIUr1AFZRg7vHZZ+jF3x9I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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