SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e6ac084ccc8053f54e693cad2e28126c2fff2fb895f1c707e8f822c00a44336' 
  AND token = 'y0tfOiDXmBZEMMTZmEJOWz5luZfV/TN6kIZhakcWLoQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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