SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bec9af74d814eb32bd4e3a18c082c6b0e59b859b826bbc5ac9560563adf08757' 
  AND token = 'G5tYrBVJtfHehQxEL9Wlk/C3aUAscBcCo8xZK7gpSB4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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