SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2bee7651ee6d20de7537985387cde0c8c7f5d57296dec324379e3dfb9ef3641' 
  AND token = 'wf3MgwBZeEoQ3z0Y6mxzudDkOn1hr76BPdRXnpXMXrY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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