SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5e5f76a2c7dab66396c3f558d786ce07d1e3291aadb4072c8b16b2e25da14f52' 
  AND token = 'U+Az2VKICLuYbOaMw6hNJcrXaUNkQ4klJdF/BlUqSUY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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