SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e608373551591ab6d15a52fdca784ddabe3a671ac080969509064cba863b4a2a' 
  AND token = 'RLZkEtqF3K2oId9Frpdf+xj3iUtysq6eYSGb1G/p584=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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