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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c6befedb6d81e50c4bb2381ea4b4d2e7cb695361dfc42cbf02e42aa5e886e5d' 
  AND token = 'eDfgmN17As+zJl/mGdueR3TOtsZcj/KaYCqg6rK2djA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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