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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5082938088cc1ee2dc4c229538f9b998fd20340b39d74a10c1e0185edf0d2a78' 
  AND token = 'NRh3cT3qPR0+ZSm7Yp0BvM6MW5w8ZZm6+CMMFi1qAg4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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