SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9a3091f22cb98be470fc1b0dac13eaae4338705795997f74e5831b703075494' 
  AND token = 'Pnjpmi1IC/dvYauUdW/LLlKD2bJ2UtYgXcfhdYsxSN8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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