SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '739f6928d452fa24809f881246f044ad71f5cebaf1572e5896c03eb62633d345' 
  AND token = 'Z52hvIOD3Patu2FZqNkPd4A3Oix2KWWVMjgNz0TDInY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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