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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55b748bedfe4b14cb6f826a94e7958d2748bd9343e986542e4a5901f7b72b0d7' 
  AND token = '4QDGVpwdFkJqwTXGZ5bXC//nxktreATtiey9azccrpI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

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