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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '577ca58ad238c0c3dcf0d983bbcde0efe1b89758f0251daf4382cc3fee7e62bb' 
  AND token = '/TQ4/7iMrwl0cN6Z8n9Q6sdhwZ5qfu+Z1HmK3yjePUM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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