SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52481f566c61dc4fc55c354d1c8a91f8573cd126c180a2776eb42822ef1e1816' 
  AND token = '/YUBZEHcAg9nnkUs2obcQ6uKMDY3LtBWNFYnVYjkJD4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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