SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39517769960c7465fdce01dd2eff2b4481d789239539a80357c642b5aeddd764' 
  AND token = 'DVphrobtETcXpIpCaEZbQHRChfJikgUvAxvaFhHBCJs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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