SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b29718c94df7012280a4207020a38643bbba6984344aa79b39435059d10f1ad0' 
  AND token = '1LjkohXSqQlScUmOylKAsJSu7XAQFru9CPhnBjDzOs0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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