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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3c5988702aa728b402c5519c4be02810f6b8d584df7d3989bcedb9d192efab4' 
  AND token = 'N+rFIrI4rYb4KVV7rqEqu9LA2Q8knRXCLzsMLn/PGk4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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