SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9db5679e6dfbe7eca3b64bde0ff4fbf50e40a2a1f654cf620b51a94bac42036' 
  AND token = 'x+cZbYYD5aJjSewdwC/ntLXdzfXRxAEWIP3ZsEUJSGA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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