SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2fcf32eaf3615b242a18af29e20b4f667a8423c8d936a0718f8937cb9dac62d' 
  AND token = '1ljbE00554OzH9Y3l6XEBohGMgl7UF2QRz1RONtCk04=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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