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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76f7a6d00db48cf2c33a6cd29260899608e82dd7ecacd6ed480280395965fc0c' 
  AND token = 'midjL34rynlcSD7fkSBRYCgCvd4hPUpRxmniNamUqC0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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