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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a621aee549e624450cbf942fb1dce5798dbeb94d2c644d66453704a8d86f6760' 
  AND token = 'AcI6BjZpT4WrPet0Cjh1gIDKgCqq8wSoAP1mZ+tfZ7g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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