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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50a28ac33755f484b9bc6e9480581570b6c31f68300f67c81712ed18b55a90d7' 
  AND token = 'zEJp/GS6RaFMieJbUSQsNPg+57+2Z84IYpO+DHCEJmA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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