SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2c94648a739e7eae7cbe56dd614f6af808f717e014b580cd570045b9eedd0e5d' 
  AND token = 'gErnTvieRbYWn2mS36m5HBATifjNm098hpe7404ZvT4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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