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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4a6524936ad76fd285687da7a6e0b7e5e218eb827b32d1de4f75e37e18e7580' 
  AND token = '4PUcz+yjwdTnt1WyEPSVmQPRXRqmae2gTN/zqjJ02w4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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