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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e5a46d708b0882d6e8a5620b1a066eb66e207f323f28641856657ee8b12bcc8c' 
  AND token = 'ZuZ2Ck8mpXEJCZ36Z7ZDC1Bee+VdzqCkiym7JU1RbO0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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