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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ef398e87be6455e42aebff75e442a84d53bf59f95be69b0e67f1403fc681983' 
  AND token = '6Lzk4REJPRviukW30LIWzoJvtbXXRPAhyT1GkXmt6m4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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