SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d5fcdb9c157968800b3a3b2d46204afd78a9ed5cbaebed9394a17acd9143e06' 
  AND token = 'VssC2ZvIfpTOzlAiBrjDKr1ycnAOF5yZHz7CoSkY7Ig=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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