SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '042236715c357363aabcea72522bc836eca029e882dfcdeab3af6e1caed8a4cd' 
  AND token = 'RNUlZNcJ7hTZz6JPSQ5hawQGQBa/LfjVB9MTfPXfPg0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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