SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a31f713619296ef3dcc9deaabb9ceb3858c278a68871dc838327dd383f5a8b2' 
  AND token = 'SLPaGsW7qfXRB66Sz+C5SD669gxnYuKj6B6oAcV0Axk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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