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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a1aa5ba147057198f2b01caf584b25c28b5b8bd4dbfc50c78fc8725608c7ff' 
  AND token = 'iZJ6zuZqGU5xQ84QRhKXXjcTSeV4zco+5gAhrsUEI1w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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