SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '608c247e4d5d1bd6cfdea93f4924ac2dd6e675c25edc732a7138637d68bec872' 
  AND token = '8TVaHIpF+Wkr4PnBQrd8CTsOJl0NfBJIpgSsQheM5dY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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