SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '298c4a1b4a2e768bc2e89678fdb1095b7c7cb3531d166f998b0cc8856da964cf' 
  AND token = 'Y91fq5T6gfDw1n8wZRMjoJMJBw6zyFyo+TgYkVPrqDY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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