SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '188418b220876983d55b87e4278059e4a1da04068ee047a11395ca170b8beec3' 
  AND token = 'IZSZBsuxGeXn1qkYCce3dfG5FjAqVI5kRwN8DvITQf0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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