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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e9acddc81b2f06240e5f50dd8615c1f24e45b456049baa956d7abb983a25259' 
  AND token = 'W3nwz61fBrEemc4smngQfAMzMVlDNV7PnoUMq0EWAOs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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