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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6bd2e2d7f57a56f3f9540e7a0318f434191dd9feb5a8de1f350bc17cae3c4dc' 
  AND token = 'UsFLVtZ1JD+HoR6Tmi8WlHLR6fqLY1MAGTQNwH0UGxA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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