SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e29ba9bb5d4b3dfa9f873fc3be9881b9618048a994badd5c1c9f4309c5ecc49d' 
  AND token = 'JgVtvtxv5sr5+R5wEiFsxBLO+tArNoXgWaanUW2up0w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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