SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3428954de752efdfce23fbe1049a35b606b6fef6a2356e81cc194bfeec14311' 
  AND token = 'gXirTiObnUWkCXTnchF+hg3JSXZ9hWJ/vujsDBqLpS8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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