SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3be8ffcfee067893627dccc7a77a0849ee1d11428a1a49f9b5578cfc520993aa' 
  AND token = '6om8v2IUEAQlxkrGUz8StwzmpgyhxRPJA/2JYAp3du0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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