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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5d1b391e4728a16c8b49c93b7ae6d2b3b9d76c5af1ac3e6442335a5e9966afcd' 
  AND token = 'PQQxuVUvDYdOKcFJK8kcKTH+O4leV2GyEOoTLbJlER8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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