SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '594cb23477632a4f3f7653365eeb8d13750b069383b6137529a7053e28cb389a' 
  AND token = '1YGvNr7xFpEAryVA4vQEynZkySS2eSNFs4kbqukk3mY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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