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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a808b1d21d2fd1070c117ea5ce5f6874c3dbbfbc75ed5c5243594f12b63610c7' 
  AND token = '99eH7yjs2Ir4g6WyUrfayjmqcWBE+9zkahVGUM7Sj1I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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