SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3385b6e823aaef9c1367294133406aefdc0038327aa202e90a3bced1b9921dea' 
  AND token = 'mlSdYjuPP1kBmatzOWDUbnzo9+LH1fpg4m0TD3YSJnw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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