SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '712d2273d63e38a346f0f0a1ce15bd98bec49ced833f6562324bc71331977470' 
  AND token = 'IrIz2gcCsbvVHk4T5IusQ6xE1hCuChOFULQwaDM9uHk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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