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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7544018e232846e022424eb22930885e6deb68f32d2c89f1c15749ed3a1ad3c4' 
  AND token = '6PGU1AiIWwP+eShebCYeYqdWwbhzhouLybjCoZ7dYew=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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