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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e9d5811f8c4cf85e4b7c3759b834964e46e4585b3afc418b8c37d720478e363d' 
  AND token = '6UhIs5k1VQDLhr0nCI/rzDDeTcTPmm+DesA97rb/83Y=' 
  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"
    }
  }
}