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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '16d8b21cfbfc61e0d8b960ffe768706572f5d09705d558b84a9bee0553b34a26' 
  AND token = '43/bATxaKUdTRaOQQbUObvFAf6CASV4fZwTtTNYqCb8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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