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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '951d44ec28a79de9af5d186b4fa252cd99b59ebd9d301df6bf5d00fbcb1c7ca7' 
  AND token = 'cEfrZa0w/cF8ywKUuBxIaQRuthRnqMUG0syz0aawArU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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