SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '257ec18d1f62fdcdcb4f64baa93680478d979e322041eefdaa6cf157576ab905' 
  AND token = 'jNGUUdh55im1/PRpAWLA9ACEXP4edvaqCBwOfGCT5cQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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