SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b75032ad473009cc62ef72d5e98594d3006973afefc3a9b58fe7dccaab61a1b' 
  AND token = '/UNS8XQlroHGETtjaBxVHoD5S0liMNTjJZ4TE+33Nz4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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