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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '426e1735657769a3d54b8053fd9f6b36dfe231fa10a0e3d00e4109637e0163cf' 
  AND token = 'D3Yy8ZiW6qoJHQ+RYymAOu0c5+BcZpMQiAiEvqXPM1U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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