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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b21a3ba35404a2e6491f0f3c83463612df46926e2ce93a11071d3e2a2ac3ffd3' 
  AND token = '9SNtyo1t8HuW2tf+XHY8Q4f2zpeeaOzYs7blP7nIPxc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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