SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2cd00cb8caf723928ddb79250d2d526c048a87c14ee3ca0451f73ae14456d559' 
  AND token = 'kVcmEafWrLgynxIlmWi+ibRVbn+hOzywPKPacVcZGUc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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