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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b52e6dc5e5e58b993d6f183337184e62b9d768e8721867ff0517e749874a2a0f' 
  AND token = 'siUD9f+RL38wb2b8yqzUCKfbl0RrlOdnaFjBQZY5oR0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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