SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76a7143bfabb1f875145eccb187c6e7afc5d12d5836b11a2a547ac7ac05611ca' 
  AND token = 'ZiFOLPcPyWg57FKdgidMhfmnrxZmj6jLPNdWnSM/4sg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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