SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8200eb7d850340eed6862cad3d3959638e9fea76376adb42acdb6dfae252746' 
  AND token = 's0a0zLY9ecso8UtMIb9cYGGPhoqoSRHVgax2YXd1Vik=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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