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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ec3b7260b8c31fdbddffab74ef3d2a3e5fb2baf1107f6de8d3e32c6300e709e4' 
  AND token = 'SzQiWoQb3adxE1bOBGfDRr8KTdTjc/jCsR4YApzoxQM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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