SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f6d9988476534a7bfe3de5779114687744307e2792322c8fe4326f6cb410c18' 
  AND token = 'ViZbXFfyVSDOT3ydXOtcASFyHxCYS+tjSUZqEP91IhM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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