SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f55a819dd51bbac137037a43d4e5cc6a2da3c7ed3a9c0a0a7d00edc43a281a8a' 
  AND token = 'dituJJYv+gieIpf/581BIKS6zMUGPWLhgyf3USZguIY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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