SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50679a683efbc85ba29300d33c9a9c0b4d56769e90bf8b8020727105b41f55f7' 
  AND token = 'i35GthBbIS6s9f2LhzCKJmjtr/dGFCPRxeQXLQyY0wQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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