SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6af42cb50017dd76a8b77f5f05176d6c5dc87a0c57f36b7eb51788f59cac1b81' 
  AND token = 'aTbA6UTqGjVeHKa+1FK1rClyDBRhrwABi3+kMUSYSek=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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