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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6f386b2670e4eee33c6c7bc2df770e2f09308e81a4d357cd0795c977c8e3a71' 
  AND token = 'CF19HSG6iKVBo/MtPtNlksT5o0mkAUHzzajEEuLSTSQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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