SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a73490d756952bd7f9d96831a49521de3dba2867fb9213dac403f26e909672' 
  AND token = 'F0AoYNzDLrdpOExe1cyl/nQAXGwOgmqgzqSjHOVgNYg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}