SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '912e62b89a38298c32fff3ee5febae500b2893ae6ecd0a644175aea22077156c' 
  AND token = 'OQ3cT5V0Smf00FgSMrp4LGhmxR0vIZDM8QZKehXZJ38=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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