SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bb6ba5f44a097a8b32d7e9e196ba270179a059a573397c57490d0d14802b5a03' 
  AND token = 'zvjV6+qQkmZ7/AiJlCtu02kuZK2hNwiGrLplVIHH3jc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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