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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76e31709b2d80486989f1860b33da412547ea06837868ab704fcef02d17975bb' 
  AND token = 'BrFbmNZPMpFobf9EM/1fZM7VEiwRYSxlE1N+sH1AFmo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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