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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '08c991bd9ef356338d8ae6e764f2330542fe0317c8e9007a5a09bed8a00a11d8' 
  AND token = 'z91gud3KdQxKrzD2TdUhHdmfzTXjSUoV3oOdPE+ZgOc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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