SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b8f1fce4573698a443ffc9a03333f3167953a287e4529331701163fb861b37e' 
  AND token = 'NFCsuCBRphSqiNm7h+f8BlDv6yfEVsSpGzRJnYslsNQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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