SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '236a86c0dc15127728b8369265ac7f502a35526eb16f6351f3f7d41b83919980' 
  AND token = 't6vUBOUvnLrDVMA8BaDuhvpBvj9WOgKph6k1uwPQEq0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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