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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a42e5b53e0840ccbd513bd166d0a87aa3775d90a634f1c5f8bc05f4a548a0b38' 
  AND token = 'yxnX6JTpVBTfFm9XPzwVV0UieZwT+Io9WvDfTfT/0Ks=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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