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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f541135fe9ad31b3da05fccfed5b8ebef3dc2f1bafcb61c2f615dbe652a64f2a' 
  AND token = 'u3kasUgSVUiq1cveDRlwj1kuxEBPSyytqit8//y5JxU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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