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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21d6812affc829100f050bc64e10ad189d90cba8d91dab820efab955619fc4d5' 
  AND token = '+F1rECLMRBaahAcO3lKSZ4+aUZFd6mq5E11v7VMthSE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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