SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8b5e246f9552e21802b50ee57268f4e044f40f49f8f2ca59bed81ae1d8cd4dc' 
  AND token = 'H8O8s7S+bIZrTQuaR2MvvJ/4RCB+tyd0UjY7iUiWP1o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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