SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7aca2a61481c3659706255b1c768256c34399155b6c7a355e69aa2389d9d9966' 
  AND token = '/7ZrEmOVCE+Rm5mrBendjNi8tdryifCwTCmbRhoMdsI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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