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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4a639a989d4a26eafef0c78af0f51c560daf3e11d8ed853993ecce1be096fdaa' 
  AND token = 'f0GjIe/jfl3HWr5CcUOZBK4OeQDJ8rv1QqdT3qorQqc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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