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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c92779535046bffef28ff9daa81c4a3a4e09bb1e631037b22a2bc54068cfd798' 
  AND token = 'DVGa+4EFny1GZayWsvWUL7WNj45ST60L5SniyzrEjMA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}