SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5921adfdf32800b124e05e8c2326a4e57512cbf3206957ce338977a55a143255' 
  AND token = 'ZKnod/kvkE5H9ARaKNRlzbPILn2nfYKqPKHQlK4qDJg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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