SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f0ef4571ce55be256020b1aad981eb0d84dcb803da6f61af97e98687ff9ec3a' 
  AND token = '4oD29NDJd6bZKjY/MYXnoiEfbhD2gqgrQ2lK1WzvJzA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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