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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51ddca1b981de385ec258674352fe327d29e952e1eb1c09e1424e555d14f4a69' 
  AND token = '0OTjP9Io8fLvJl2C7236ElexKFURyO0cnOc21jhV4mw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}