SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75b76c4f6532cd07bf61bbc12fbe5c47d51d16781c92ac451021f7ce02deeafc' 
  AND token = 'zQowJssCOiocJKVDK+KbW7SQKsYmdGLW3CFaxeccKM8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}