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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6868998ac8140de0d6fa8696f9fea20476c1bd3bc07cbed43b42d165b9bcfe37' 
  AND token = 'ejF27MqBN4KeUpTEJqBLdRQbvUlR1Kzgzvlby+Q+ULg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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