SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '936b2308e816397573dd867bf682eba81cf3abb866ea1689d0a6d1120e4e7471' 
  AND token = 'oZdKRpslExjAZd3BWDVnbdu7ILOZzpWSAfIonB8ktZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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