SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '312b96e3bee5aa0b1eaa577dfd8cd9cefafed6bb126999b9659ca8b6e5275c42' 
  AND token = 'FpVMo7clxHvZHsP83GcZApnNZUFtqPy19HTmLUeVTRs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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