SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '28839ee76fce28c9624e1c88a2abb785e6eee9900d8b3be5046bb41d5ad05f89' 
  AND token = 'V1YA8JLkSu7Liav0CmhT2MSfWrKS0duSzKhTLIxRWKY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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