SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6921650c556f611ccc0eae19a694073ab953c737c173c9d793e91aa494a1829b' 
  AND token = 'zSQioMJ9Sk3stQQkxpKNoW1OBW6ugdMnANTB+oGP30A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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