SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8df6fe8d2d73fa21f23a726dc6975a3f13f2a31fad68a57e21ea2ed13c70ca38' 
  AND token = 'hL+DrL6d1CEjw5kfMAXiBZP6onGrJW0slcHLfyEttXU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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