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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1758bd915edc23667ab0a7aa4c566048c4b248dbb4f53232cfb1ecaea0c3ca4' 
  AND token = 'j0qVxJtOLqqF57XvgSxwzgQM4bFAGd3TH1gxcy+ASD4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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