SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cd843a8397a99f959207f463a117c12922c55dc38f963795802319a7774d8bde' 
  AND token = 'kxNgw11HCnFYnaGMMYje4Ksc+3sSEEU5v0CfDzGCb4U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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