SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a76caa10a2dfbb0c45e7ede684770cd6f7d5efdc81277f746ee391e731139411' 
  AND token = 'vPNSAdvYpHUy1WCG5lffC3IqsfGlzhmIvFJwnd9JqfA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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