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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '38b9ad4ee7f29992c3b0de5beb4283f09f8051e3d4918d3e9f4d4238462b5fa9' 
  AND token = 'fzUn56kOIQ8ZMXTphV1nqlIk0Gf2zLWcYzqlk9WnemU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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