SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'abf7f068a3df761867cffdd0278d9ce60e8a2506161fa451d3fd5729d1c88d40' 
  AND token = 'fud/AUPmorwjFmOAJOSRhQXdKcdptTwYWl4Uc/rBN9A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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