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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55e29841d9c5b6cd28098932a8d926fa0a0a9b6b59a13adda0debb98fa3e6814' 
  AND token = 'KwZ/hXSSope0NhN6zHTIwEPXDwIyvAUAniCQfKWu0uw=' 
  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"
    }
  }
}